The large black Fitbit charge activity + sleep wristband helps you get motivated to be more active – it tracks how many steps you take, distance traveled, calories burned, floors climbed, and how many minutes you stay active. The OLED display lets you see your progress in real-time throughout the day. The built-in rechargeable battery lasts for 7-10 days before needing to recharge. Built with caller id, charge shows your incoming calls when your phone is nearby to help you take control of your day and your schedule. The charge also tracks your sleep at night and you can review your trends on the dashboard. You can also set a silent vibrating alarm to help you wake peacefully. Sync your stats wirelessly to mobile devices and computers. Simply download the Fitbit app to sync with a smartphone, which is available for ios, android, and windows phone devices.