CES 2013: Hands-On with the Fitbit Flex Activity Wristband - YouTube
Fitbit Force review: A fitness tracker tour de force - CNET
Fitbit Flex Review
The story of Fitbit: How a wooden box was bought by Google for $2.1bn - Wareable
CES 2013] Fitbit Announces The Flex, A Wristband To Help You Monitor Progress While You're Up In The Gym Just Working On Your Fitness
Amazon.com: Fitbit Sense Health & Fitness Smartwatch W/GPS, Bluetooth Call/Text, Heart Rate SpO2, ECG, Skin Temperature & Stress Sensing (S & L Bands, 90 Day Premium Included) International Version (Graphite) : Electronics
Fitbit Force Flips the Bird at Early Flex Adopters | GearDiary