The Benkyou app for iOS and Android lets you study kana flashcards with an easy swipe-left/swipe-right interface. And plugging in your WaniKani API lets you study even more!
Using Benkyou is straightforward: from the home screen, choose hiragana, katakana, or WaniKani. For kana, check the rows you want to review, click "Study," and the first flashcard appears. There's no forced input, so simply say or think your answer, then tap the card to see if you were right. If you were, swipe right — if not, swipe left.
Connecting your WaniKani API adds a whole world of flashcard-swipe reviews.
Connecting your WaniKani API adds a whole world of flashcard-swipe reviews, including radicals, kanji, and vocabulary from all levels, as well as your critical and recently unlocked items. You can also study burned items to see how well you remember them, then decide if they need to be unburned and re-added to your queue.
Benkyou's only drawback is the lack of forced input, which is our preferred way to study flashcards. Still, if you have a few minutes to kill while holding groceries in one arm, the swipe-left/right review system is a quick and easy way to study.