Me too, so I gave it a shot myself inspired by the many Med students in my area. I started with a Mac app (Flashcard Hero), currently working on an iPhone counterpart with iCloud sync. Tried to keep the interface as simple as possible. Cards can only be rated easy/unsure/hard, the UI hides the actual algorithm and marks cards from red (very hard) to green (memorized).

UI: http://flashcardhero.com/screenshots/ I'm always open for suggestions.