I introduced my class to the Bedtime Math app last week. Once a week, possibly more, students will take a screenshot of the day's math problem and import it to Skitch. They will have a choice of the "wee ones" or "little dids" problem, depending on which they feel better suits their abilities on a given day. In Skitch they will show their solution and answer.
I really like the levels offered by this app, the plethora of problems, and the real world situations they're tied to.