The best "app" I've found is a DS game designed for Japanese speakers : https://www.nowpro.co.jp/menu/products/game/kanzen/

Everything is in context, it has a practice portion for things you needed help on, you can make lists of vocab, it tests for kanji writing as well as reading, and the zatsugaku challenge has lots of interesting things going on.

I haven't found any other tool to be even in the same league