There's several good kanji apps for the iphone - I think I have downloaded almost every Japanese app on my iphone
Try iKanji, Kanji Flip and KanjiPop for starters. The system won't let me post urls so just do a search for those in the iTunes store. I have used all three and they're great.
PS - I have a couple of DS kanji games too - will post more about those soon for you