It's a pretty well known fact that, when trying to lose weight, you have to create a caloric deficit -- for every 3500 calories burned, that's one pound of weight lost. Thus, it takes a combination of diet and exercise to create said deficit. However, it is exceedingly difficult to keep track of your caloric intake, as well as calculate the calories burned for various activities. If you're serious about getting in shape, though, there is a solution: using an automatic body monitoring system like BodyMedia's FIT Armband.
So, what does this have to do with Android, you ask? The BodyMedia FIT has a corresponding app in which it communicates with via Bluetooth, making it even easier to monitor where you're at for the day. It monitors your caloric burn as long as you're wearing it -- day or night. The app also offers an easy way to track your caloric intake with its food logger. All that data, in turn, syncs with BodyMedia's servers so you can easily keep an eye on your overall progress.
This system, normally around $250, is Amazon's Gold Box Deal of the Day, making it available for $140 with free shipping, which is a pretty solid deal for a system of this nature. Hit the link below to buy.