The list will go with a name of the app, number of problems along with target/difficulty levels, price, link to AppStore, and my (or other's go players) short opinion of pros and cons of a particular app.
Newest additions are always at the top of the list.
I hope this list will be useful to you. Please remember this list is permanently 'WorkInProgress', so it will grow over time.
[previous update 30.XII.2013, 3 apps added, changes in some descriptions, corrections]
[last update 14.III.2014, SmartBaduk/Yoo Chung Hyuk info update for iOS 7 users)
Recently added apps are at the top of the list.
A legend:
DDK stands for double digit kyu (beginners), SDK - single digit kyu (intermediate), Dan is master level (advanced)
(23)
Name: Tsumego Pro (Go Problems)
Number of problems: 712 (178 beginner problems, 211 elementary, 50 easy, 145 intermediate, 128 advanced)
Range: DDK to Dan (?)
Price: Free
Link to AppStore - None
Link to GooglePlay https://play.google.com/store/apps/details?id=net.lrstudios.android.tsumego_workshop
My opinion:
Looks like it has very nice interface, but since I don't have android device I can't say anything more about this app.
(22)
Name: Go Game: Yose
Number of problems: 727
( 174 官子价值学习第一阶 /basic, 39 官子价值学习第二阶 /basic, 106 初级官 /easy, 309 中级官子 /intermediate, 99 高级官子 /advanced,)
Range: DDK to Dan level
Price: $4.99
Link to AppStore https://itunes.apple.com/app/go-game-yose/id673691591
Link to GooglePlay - None
My opinion:
Third app from developer of Go Game Tesuji and Go Game Life and Death (both mentioned below). Looks like quite good collection of end game problems. Every problem has description in Chinese but it's ok to ignore it - every time it's black's move and a goal is to play the best sequence.
(21)
Name: Go Puzzles
Number of problems: 300
Range: 100 DDK, 100 SDK and 100 Dan
Price: $1
Link to AppStore https://itunes.apple.com/us/app/go-puzzles/id690639727
Link to GooglePlay - None
My opinion:
It's an interesting app with kind of new user interface approach - very simple, but presentation is nice and clean. What make it different from other apps: you can't play any moves, you need to work out every problem in your mind. Correct and incorrect solutions are presented with no distinction which is which, just remember the first one is always a good one.
This is a compilation of problems available previously on GoGameGuru.com. I contacted developer of this app and he told me these problems are on a site with CC licence so according to him it was ok to use these problems. I wrote an email to David from GoGameGuru.com too for clarification if it's really ok.
(20)
Name: Cho U’s 4 by 4 Go Puzzles
Number of problems: 100
40 Beginner, 30 Easy, 20 Intermediate, 10 Hard.
Range: From complete beginners to high dan players (approximately)
Price: $2.99 /+ three additional sets of problems (50/50/100) for $1 each.
Link to AppStore http://itunes.apple.com/app/ri-ben-qi-yuan-zhang-xuno/id517153034
Boidhre's opinion: "Very nice. The Intermediate problems I've done are nice little ko problems with loads of traps in them, that move that looks really like a tesuji results in a ko six moves later and that kind of thing. Fun! (...) The initial app is expensive for what it is but I don't know of an alternative if you want a set of 4x4 problems on iOS and these would be ideal for solving solely in your head as John Fairbairn was talking about in another thread."(see here: http://www.lifein19x19.com/forum/viewtopic.php?f=15&t=8427)
(19)
Name: Go Problems
Number of problems: 4797
(228) taken from goproblems, Xuan Xuan Qijing (34), Guan Zi Pu (46), Problem sets 1-9 (4382), Igo Hatsuyo-Ron (11), Carpenter's square (14), GoSeigen (82)
Range: ddk to high dan
Price: Free / $35 via In App Purchases
Link to AppStore https://itunes.apple.com/app/go-problems/id635778548
My opinion:
The good : nice interface. And it's the end of good news. The bad: pricing. Every set cost you about $3. And you can't be sure if Problem Sets 1-9 (the root of this app) are any good. All additional sets (I'm not sure about Problem Sets 1-9) are available free on the internet, and it is rather hard to find any justification for the prices in this app.
(18)
Name: Life and Death of Go
Number of problems: 7329
How to calculate liberties? (44 - some theory of semeai with diagrams)
Classical life-and-death shapes (118), Entry Level (800), Primary Level (800) , Middle Level (752), Superior Level (753), Kensaku Segoe's (950), Lee Chang-Ho's (738), Secret Essences (264), Fly Dragon Diagram (1000), Moving Finger (136), Magic Chess (446), Fa Yang Lun (193), Maeda Nobuaki's (210), Kada Koji's (216)
Range: DDK to Dan levels
Price: Free / $4.99 via In App Purchase (this is not an universal app, purchase on ipad cannot be restored on iphone, however you can use iphone version of app on ipad)
Link to AppStore for iPad https://itunes.apple.com/pl/app/life-and-death-of-go-p/id629031949
Link to AppStore for iPhone https://itunes.apple.com/pl/app/life-and-death-of-go/id623698040
My opinion:
Very good app from developer of Tesuji of Go. Both apps share same interface, it's clear and useful - looks ok on a phone, but not well designed for an iPad. The only downside is that it does not mark solved problems and there is no thumbnail view in a list of problems, only numbers. But if you are serious about studying L&D or Tesuji then you probably do your own journal with all data what and where you have completed already.
There is very interesting section about counting liberties in semeai if each group has an eye. There is presented some theory about "level of eyes" and simple calculation method which can be used to speed up a process of counting liberties in semeai. This was quite new to me.
If you have "WeiqiDB" app you can find that these apps share some problems library. I can't verify all problems but Level1 in "WeiqiDB" certainly has the same sets as Entry Level in "Life and Death of Go". If you are to decide which app to choose I would recommend this one over "WeiqiDB" (which has really terrible user interface).
There are a huge number of problems to solve, interface is good and a price is low so I highly recommend it.
(17)
Name: Art of Go (Collection from Master Wu)
Number of problems:81
Range: kyu/dan level
Price: Free/In App Purchase $1
Link to AppStore https://itunes.apple.com/us/app/art-of-go/id579972595
My opinion:
You need to speak Chinese to get the most out of this app because it is almost an audiobook with limited interactive section. It is some classic set of problems but I can't read chinese to be sure what is it exactly - probably it's a collection of Go Seigen's problems (there is reference to Wu Qing Yuan in app description). The app is Chinese only and every tsumego has full voiceover with position playthrough, which means you will hear a Chinese lector telling and showing you step by step how to solve particular tsumego you looking at. Very uncommon way to present go problems. There are 60 problems for free, and next 21 to buy for $1. Worth checking even if you don't understand Chinese.
(16)
Name: Tesuji of Go
Number of problems: 5 333
Authors/sources:
Jin Jiang (267), Tom (366), Kensaku Segoe (188), Lee Chang-Ho (735), Japanese Go Association (2 636), Kudo Norio (101), Yoda Norimoto (202), Middle Level Tesuji (360), Fujisawa Shuko (228), Ishida Yoshio (250)
Range: kyu to dan
Price: Free/In App purchase $4.99
Link to AppStore for iPad https://itunes.apple.com/us/app/tesuji-of-go-p/id629122102
Link to AppStore for iPhone https://itunes.apple.com/pl/app/tesuji-of-go-game/id622584811
My opinion: Looks like another very good package of problems. Interface could be better, looks ok on a phone, but not well designed for iPad. Low price with a huge amount of problems to solve. Sold!
(15)
Name:Igowin Life
Number of problems:2000+
Range: from DDK to strong SDK
Price: $2.99
Link to AppStore https://itunes.apple.com/us/app/igowin-life/id352240198
My opinion: Not bad, but interface is limited, very simple, there even isn't any list of problems. There are L&D, tesuji and joseki problems, all mixed up. There is no way to choose special section or to look at specific problem once again. There are no problem "divisions" for ddk, sdk or dan. You solve a problem you get a harder one - that's all (you can also solve a hard sdk problem and then get a 30 kyu tsumego so it's a little random). 2000+ problems for $2.99 is a good deal, and even if you are KGS 2/1 dan you can be surprised sometimes.
(14)
Name:XGoo HD (iPad) and XGoo (iPhone)
Number of problems: many - there are added new tsumego each day -> infinite?
Range: kyu/dan
Price:$9.99
Link to AppStore for iPad https://itunes.apple.com/us/app/xgoo-hd/id508416256
My opinion: Very good app, worth it's price, but it is not an universal app so I can recommend you only iPad version which I have bought and use. It is very interesting app: there is huge online database of games (over 100 000! but not easy searchable, internet connection needed), huge number of go problems but also not searchable in any way (you can just scroll infinite list of them). There is fuseki pattern search engine, which gives you exact games. And there is ready made compendium for some specific fuseki which can be very good for study. You can have multiple games opened at once (as well as multiple tsumego) - very nice feature when you study specific situation.
(13)
Name: Magic Baduk Go //iOS + Android
Number of problems: 1450
300 Begining, 300 Intermediate, 300 Advanced, 250 Expert
300 Tesuji
Target range: DDK to dan level
Price: $2.99
Link to AppStore https://itunes.apple.com/us/app/magic-baduk-go/id411378862
Link to GooglePlay https://play.google.com/store/apps/details?id=com.bdapp.badukmosueng
My opinion:
Good value. Lot of problems to solve, low price. Simple, useful interface.
(12)
Name: Master of Go //iOS + Android
Number of problems: 1200
100 easy (DDK), 402 normal (SDK), 440 hard (strong SDK / low dan), 158 very hard (dan)
Target range: DDK to dan level.
Price: $1.99 /
Link to AppStore https://itunes.apple.com/app/master-of-go/id412842099
Link to GooglePlay https://play.google.com/store/apps/details?id=com.maryharry.masterofgo
My opinion:
Good value. Lot of problems, low price. Useful interface.
(11)
Name: Nihonkiin Tsumego Master
Number of problems: 485
25 before start tsumego, 25 intro (DDK),65 beginner (15k-10k), 60 intermediate (10-7k), 60 advanced (7k-4k), 55 shodan,
55 micro tsumego (Ohashi Hirofumi 5p),
55 simple tsumego (Rin Kanketsu 7p),
55 pearl tsumego ( Shinji Yamada 6p),
55 higher level tsumego (Toshimasa Adachi 2p)
Range: DDK to dan level
Price: Free / Additional sets of problems available via in-app purchases $3 for sets of tsumego composed by pro, $1 for each set from "beginner" to "shodan". Total cost of $16-25$ (may differ in some regions).
Link to AppStore https://itunes.apple.com/us/app/nihonkiin-tsumego-master/id483504917
My opinion:
Good interface, and there is always a free portion of problems for each level so you can try if they fit you. You can see a miniature of every problem set so you can decide by yourself is it worth to pay for, or even you can try to solve them from a locked view. Overall it's quite good app but an additional in-app purchases gives you entry only to a limited set of problems so it does not goes cheap at the end. It's partialy free so give it a try.
(10)
Name: HY’s Creative Life&Death Problem
Number of problems:393
50 (30-18kyu), 49(17k-15k), 35(14k-12k), 30 (11k-9k), 31 (8k-6k), 27(5k-3k), 27 (2k-1k), 25 (1-2dan), 23 (3d-4d), 24 (5d-6d), 32 (7 dan), 40 (Pro)
Range: beginner to pro
Price: Free
Link to AppStore https://itunes.apple.com/us/app/hys-creative-life-death-problem/id571906462
My opinion:
Good value. Problems for everybody. Interface is far from perfection, is not well designed but after a few minutes you will know how to use this app. Beware - a few problems are incorrect. It's free so give it a try.
(9)
Name: Smart Baduk Go - Full / Yoo Changhyuk Life & Death //iOS + Android
Number of problems: 1800
300 begining 1, 300 begining 2, 300 intermediate 1,300 intermediate 2, 300 advanced 1, 300 advanced 2
Range: beginner to 2-3 kyu EGF
Price: $5.99 - read comment below before you buy
Link to AppStore: https://itunes.apple.com/us/app/smart-baduk-go-full/id487100814
Link to GooglePlay: https://play.google.com/store/apps/details?id=sgdata.baduk&feature=search_result#?t=W251bGwsMSwyLDEsInNnZGF0YS5iYWR1ayJd
My opinion:
Good value. Interface is good. Few seki problems with opponent's last move are messed up (you can't complete them). Overall it's a good training tool.
Attention iPad users: due to some bug in the app it crashes on iPad. Lite version works but full is broken.
There is partial workaround for this crash: please change Region Settings in iPad's "Settings" App to Korean. "This doesn't change menu languages and similar, only date format, names for days of the week and so on." - thx Boidhre! App should work now. On iPad4 - works ok, but if you have iPad 1st gen then it's hard to say will it work or not (does not work in my case).
iOS 7 - app does not work properly. Don't buy this app until update with bug fixes.
(8)
Name: Go Grinder //iOS + Android
Number of problems: 497 but you can add there your own sets of problems
150 basic tsumego, 347 Xuan Xuan Qi Jing
Range: SDK and dan, and you can add to it whatever you have
Price:$2.99
Link to AppStore https://itunes.apple.com/us/app/gogrinder/id391100440
Link to GooglePlay https://play.google.com/store/apps/details?id=com.gogrinder
My opinion: It's ok, and if you have your own sets of problems you can add to it then it even more than ok.
(7)
Name: EasyGo
Number of problems: 2368, and you can easily add there your own sets of problems
752 of total basics, Tsumego: 443 Easy, 251 Medium, 199 Hard, 428 Tesuji, 295 Endgame
Range: beginner to dan levels
Price: $11.99
Link to AppStore https://itunes.apple.com/us/app/easygo/id492566615
My opinion: Very good value. Quite big database of tsumego and ability to add your own sets of problems. This app is also a very good tool for creating tsumego sets, it has good go game sgf editor with moves tree, and can show you raw sgf as txt - very useful. The app looks a bit pricey at first sight but is definitely worth it's price. Check out a free "lite" version. I use it for creating a tsumego collections I gather from different sources and I use this app mainly for teaching kids and as introduction for new players (built in problems are very well prepared for this ) and it's very good tool for this purposes. If you are new to 'go', want to teach someone, want to teach kids how to play or how to solve go problems then this app is definitely a very good choice.
(6)
Name: SmartGo Kifu
Number of problems: 2044 (goproblems.com?)
Range: DDK to high dan levels
Price: $19.99
Link to AppStore https://itunes.apple.com/US/app/smartgo-kifu/id364854741?
My opinion: Tsumego section is good, but it's not a main feature of this app, and it's not that good itself for premium price of this app. There are other features which are making this app the best one. It's great as a game recording tool and for reviewing games, there are also: pattern search/recognition (joseki & fuseki/joban search), huge database of pro games from GoGoD (over 73 000 of them) with biograms of pro go players, bookview option for game review, guess next move option, very good editing tools - almost in par to desktop go software, tree view. Interface is very good, zoom options are done as it should be. There is nothing comparable on other mobile platforms, and I call this app a killer feature of iOS and Apple devices. This app is worth it's price and is worth to buy an iPad itself just for this one app (along with SmartGo Books). I bought it 4 years ago (previously SmartGo Pro) and I'm still using it almost every day. My personal Best Mobile Go Software.
(5)
Name: WBaduk //iOS + Android
Number of problems: 2633
Range: DDK to dan level
Price: Free
Link to AppStore for iPad https://itunes.apple.com/us/app/wbaduk-hd/id449564884 & iPhone https://itunes.apple.com/us/app/wbaduk/id449564651
Link to GooglePlay https://play.google.com/store/apps/details?id=com.wbaduk
My opinion: Although it's a client for playing games there is a good tsumego section too. It's a free app so give it a try.
The app is not perfect, here is a link to the post made by lindentree about some bugs in Tsumego section:
viewtopic.php?t=8941
(4)
Name: Go Game Life and Death
Number of problems: over 7000
"Amateur" section: 50, 837, 106, 610, 442, 59
"Pro" section: 111 发阳论, 997 天龙图, 1688 官子谱, 462 官子谱 2, 246 玄玄棋经, 92 棋经众妙, 136 鬼手魔手, 300 职业集一, 80 职业集 2, 245 职业集 3
Range: DDK to high dan levels/pro?
Price:Free / In-app purchase
Link to AppStore https://itunes.apple.com/us/app/go-game-life-and-death/id528519530
My opinion: Interface is not the best one. Huge (7000!) database of tsumego. From DDK to high dan level. Worth to pay via in-app purchase. Descriptions of problems are all in Chinese, but it's not a dealbreaker and knowledge of chinese is not needed to solve any problem.
(3)
Name: Go Game Tesuji
Number of problems: 3508
Range: hard to say where it starts but probably SDK to dan level
Price: $7.99
Link to AppStore https://itunes.apple.com/us/app/go-game-tesuji/id562897263
My opinion: Good value but shares same interface as Go Game L&D so it is not a pretty app, especially on iPad where it looks like overstretched iphone app . It's not a cheap one but it has a huge number of problems. Descriptions are all in Chinese, but in most cases they are not important to understand what we have to do.
(2)
Name: WeiqiDB / 围棋题库
Number of problems: 6400
Range from weak kyu to dan level.
Price: Free / 4€ or 5$ for answers
Link to AppStore https://itunes.apple.com/us/app/wei-qi-ti-ku/id578451349
My opinion: It's a good deal. Even if interface of this app is a real pain (it is the worst interface I saw in the AppStore, really), there are thousands of tsumego to solve and it's free.
(1)
Name: WeiqiOk //iOS + Android
Number of problems: 12,563
Range: from beginner to high dan levels
2024 Simple (<9k), 1728 (7k-9k), 2127 (4k-6k), 2397 (1k-3k), 1745 (1d-2d), 1480 (3d-4d), 1062 (>4d)
Price: yearly subscription of $60
Link to AppStore https://itunes.apple.com/us/app/palm-weiqi-hd/id530802453
Link for Android http://www.weiqiok.com/asp/UserHandPudu.asp
My opinion: Too high price as for me. But you get a huge database of fuseki, tsumego, joseki, kifu, players, pattern search etc. It's basicaly a mobile client for weiqiOK.com site. Payment model is the only thing I dislike about this app/service, but if you can afford to spend so much money, well, it's your choice.
Name:
Number of problems:
Range:
Price:
Link to AppStore [url][/url]
Link to GooglePlay [url][/url]
My opinion:
Just bought SmartGo Kifu after reading your reviews 
