At the CES event in Las Vegas this week, Fitbit unveiled a new Bluetooth Smart-enabled, wrist-worn activity tracker, called Fitbit Flex. Like most of Fitbit's other trackers, the Flex also promises to help users track their sleep health if worn at night. All of Fitbit's previous activity trackers were intended to be worn clipped on to clothing or tucked into users' pockets. The Flex, which is...
