I thought Proof would be a good name, but it turns out so did someone else: http://www.mindbloom.com/about/announcements/new-proof-challenge-app-sparks-friendly-competition-between-friends-families-and-colleagues-to-make-reaching-goals-fun/
Then I also found Klash (https://www.klashapp.com/) and ChallengeLoop (http://www.challengeloop.com/mobile).
If you've got a good twist or a better business plan, how about something like "Do-nation" / "DOnation"?