Nudge Kick can help diabetes patients create an exercise habit. With Nudge Kick users can block access to apps (on their phone) or URLs until they meet a fitness goal. For example, a user can set up a phone to block Angry Birds or Gmail until they walk 10,000 steps or check into a gym.
A recent study at University of Pennsylvania suggests this strategy is effective: http://pubsonline.informs.org/doi/abs/10.1287/mnsc.2013.1784. Katherine Milkman and her colleagues found that subjects exercised significantly more often when given access to audiobooks when and only when they were at the gym. Another way to think about this: subjects who unlocked access to an app when they checked into the gym exercised more often.