I haven't had time to test it extensively, but have you got an algorithm which will increase the reward points automatically for tasks you frequently skip, thereby adding extra motivation for doing them? Would make it killing.
Not mandatory, but you could look into JD's themes and customise it befitting this usecase for mobiles because such a solution will be more useful in mobile platform. I should also point you towards telmigers works which, I feel, might give you a few pointers regarding reminders.
Good work. Would watch you taking it ahead keenly.
sincerely
Riz