The Flex is a wristband-style tracker, like the Nike Fuelband, so you wear it all the time, even while sleeping–and Fitbit has a hefty sleep-tracker system, complete with a nice little wrist-vibration to wake you up. We’ll learn more about the Fitbit Flex tomorrow from the Convention Center floor, but for now we can tell you that the Flex will cost $100 and ship sometime in the spring.
