I want to do reviews for people but not sure how without a PC

How do you mean? Do you mean recording a game that's going on live and then adding variations to that when you're on the move and either emailing it to someone or replaying it on a board for them? SmartGo Kifu is excellent for this. If you mean take someone's sgf, review it on a PC and send it to your iPod so you can replay it at the club or whatever again SmartGo Kifu can do this using Dropbox. If you mean review pro games, SmartGo Kifu comes with rather a lot of uncommented ones. You can upload commented sgfs using either Dropbox or copying and pasting a link to an sgf from the web, from say GoGameGuru or wherever. You can also add comments to the game in the app and then email the sgf to yourself or whoever later if you like.

Personally I find it quite inferior to doing any of this on a tablet because of the lack of screen real estate but it works well enough.