The Bodymedia Core Armband is an on-body monitoring system that helps you keep track of the 3 essential factors of your weight loss program: calories consumed, calories burned, and the quality and quantity of your sleep. Its so small and lightweight that you can comfortably wear it when you work out, walk, sleep or do your everyday activities. It has high- and low-limit alarms that keep you from going beyond or below your fitness capabilities. Other features include target zone alarms, a daily alarm and 4 sophisticated sensors that capture over 5000 data points a minute. You can download the stats to your PC to check your progress and send the info to your friends. Its display lets you clearly view your daily distance covered, total steps, calories burned and daily workout memory. This armband comes with a USB cable and instructions that help you get started. Its powered by 1 lithium polymer battery (included).