I have an iPod Touch, and although the learning history cannot be carried over from the iPod to the computer, I have been experimenting with the iPhone version of Supermemo. It is available for free at the App Store.
Although I don't think I would enjoy using it for all of my repetitions (I usually have between 300-400 every day), I am interested in using it brush up on a few subjects for free. After I know the iPhone flashcards fairly well I can recreate the same flashcards in my master Supermemo database and they can be further remembered with little effort. It's like loosening up a pickle jar for later usage.
I think the "add x number of new flashcards every day" is a nice feature to prevent an overload of new items.