Some ideas I have:
Mobile app "Habit Maker" and "Habit Breaker" that gives you a text message or picture every time you unlock your phone ("Eat more Veggies", "Move More", "Deep Breath")
Mobile app that tracks all text messages and facebook posts and sends them to a website
Facebook app for the habit make/habit breaker idea
Web app to keep track of events & signup for ACM student group (flexible enough for signups by other student groups!)
