Fitbit Flex tracks the wearer's activities through motion sensing with a triple-axis accelerometer, as of July 2015. It automatically syncs this information with any computer or smartphone devices the wearer pairs with his Fitbit Flex. The device lights up when the wearer gets close to a daily goal.
Fitbit Flex is a wrist band that tracks the wearer's steps, distance traveled, calories burned and active minutes. The wearer sets goals for himself in these categories, and the device's LEDs light up when he is within 20 percent of a goal. It also monitors the wearer's sleep patterns, including how long he sleeps and the quality of his sleep. It has a silent alarm feature that wakes the wearer up with vibrations.
The wrist band wirelessly syncs with computers or smartphones when it's within 20 feet of a recognized device. The Fitbit application displays activities using charts and graphs. When the wearer reaches certain milestones, he receives badges on Fitbit. He can share his progress with people he knows and challenge them through the application.
The Fitbit Flex's battery lasts up to five days, and it takes between one and two hours to charge. The wrist band is resistant to sweat, rain and splashes. However, it isn't designed for swimming. Fitbit also recommends taking it off when showering.