I was looking for a goal-tracking app when I came across Pact. It's similar to DietBet in that you get paid for meeting your goals. The way it works is you decide you're going to do one of 3 types of tasks a certain number of times a week. If you don't meet your goal, Pact charges you however much you agreed each activity is worth. I decided on $5 an activity (the minimum).
For example, I have made a pact to work out for a half hour at least 3 times a week. You can either complete a GPS-tracked activity on RunKeeper or check-in to a location designated as a gym on Pact for at least a half hour. I've run, biked, and gone to my climbing gym for my workouts. I also synced MyFitnessPal to Pact to track my calories (must be at least 1200 a day) 5 times a week.
Since I'm only on a trial this week to make sure it's working correctly (it is), I won't win any money. But it's still kept me motivated enough to lose 4 pounds this week! I am definitely going to sign up for real which will put real money at risk if I don't meet my goals. What's also nice is you can "take a break" from your Pact ahead of time if you know you won't be able to track your goals.