A two-inch accelerometer­equipped sensor from Fitbit lets health-conscious people track their physical activity and the calories they burn; slipped into a wristband to monitor wrist tremors, it can even gauge ­quality of sleep. A base station connected to the Internet retrieves data wirelessly from the device and uploads it to the Web. Online, users can measure calories consumed against calories burned, or compare their physical ­activity with that of friends and family.

Credit: Courtesy of Fitbit