Menstral (http://menstral.net/) is a menstrual-calendar application I wrote. (It tracks a woman's period and fertile/infertile days on the calendar). I think it is a good example of keeping the UI/interaction simple for ME applications (i.e. adapting the interaction to the medium) as it only uses one command ('select') and the arrows for input.
The users are happy with the application (they provided translations to 14 languages), but Menstral could use some better visibility (as the number of downloads is still relatively low).