Does this actually encourage you to exercise more?
i think that if you buy into the device and all of its social aspects its that interaction with others that helps keep you motivated on reaching your goals. If you have have family and friends using Fuelbands and you are competing against them for gaining points it can be fun the same with the Fitbit and any of these other devices.
If you are the type of person that likes seeing targets and goals these things can be great motivators in getting you to achieve a goal. If your a person that likes the competing against others they can be great. But like any fitness tracking device they can only do so much. The person using has to deicide to get out and use them.
It also help me lose 25lbs. So there's that :)