Kanjiriffic is a free and standalone iPhone web-app, designed to help drill kanji using Schultz's KanjiDamage method. It was created when I found the existing free iPhone kanji apps lacking, and wanted a way to quickly drill my kanji when I had some spare time.
It can be accessed here, although this is best done on a mobile device like an iPhone. On the iPhone, one simply has to bookmark it to their home screen to store it as an offline app. There are also two sister-apps, Hirariffic and Katariffic, both available for free that are the same app but using different databases.
Kanjiriffic, being meant as a self-test tool and as my introduction to iPhone offline web-apps, was not as trivial to create as one might expect. Getting the UI right so that self-testing would require minimal effort took several design iterations, not to mention effort the required to make sure it functioned properly on mobile devices other than iPhones. An additional consideration was to keep it as open-ended as possible, so that it could be used to drill other things besides Kanji (of course this came in handy straight away for Hirariffic and Katariffic)