There are plenty of fancy body composition analyzers on the market. The ONE SMARTDIET is the most portable one we have seen. It can provide you with your body fat, water %, muscle mass, BMR, BMI, and calories burned. It combines with your iOS/Android device to help you make sense of your data.
This gadget connects to your phone automatically. It weighs only 0.7 oz and is tiny enough to fit in your pocket. Its battery lasts for 168 hours.