BETTING THAT YOU'LL LOSE WEIGHT: DietBet.com, HealthyWage.com and Stickk.com let you wager money that you'll shed some pounds. Miss your goals and you'll lose your cash.

CASHING IN: DietBet.com and HealthyWage.com offer cash rewards for meeting your goals. The GymPact app pays out money if you hit the gym when you say you will.

HOW IT WORKS: The sites and app make their money by taking a cut of the money pooled from those that don't meet their goals.