The Fitbit app (version 1.0.72.4907) is available to download from the Windows Phone Store, and is compatible with devices running Windows Phone 8.1 and Lumia Cyan. With the companion app, Fitbit is said to be the first wearable device to fully use the improved Bluetooth support by Microsoft. The Bluetooth issues in the previous version of the OS were addressed by Microsoft in the update.
With the Fitbit companion app for Windows Phone, users can easily view the step counts from the pinned Fitbit live tile on their devices' start screen. The app gives real-time statistics on the Windows Phone 8.1 device with "automatic and wireless syncing for all Fitbit activity and sleep trackers through Bluetooth 4.0."
The full list of Fitbit's activity and sleep trackers currently consists of the Flex (wireless activity + sleep wristband), Zip (wireless activity tracker), One (wireless activity + sleep tracker), and Force (wireless activity + sleep wristband).
Fitbit Companion App for Windows Phone 8.1 Now Available for Download | NDTV Gadgets