Make fitness a lifestyle with Fitbit Flex, featuring FitStar to make sure you stay on track. Free 3-month trial of FitStar Personal Training. FitStar offers tailored workouts streamed straight to your phone, tablet or computer. Fitbit Flex tracks steps, distance, calories burned and active minutes. Device monitors your sleep and wakes you with a silent, vibrating alarm. Automatic sleep detection. Set goals, view progress and earn badges with the free Fitbit app. Rain, splash and sweat-proof design.Rechargeable battery lasts up to 5 days on a full charge.