Cost: Free (not including cost of Fitbit device)
Fitbit is the OG smart step tracker, and I love how easy it is to track not only steps but also sleep and other activity with it. You can even jazz it up with some chic accessories. I'm obsessed with my Fitbit and wear it every day. I also love the corresponding app: you can log food, set and manage goals, connect with friends, and record your workouts. You can also use MobileRun to track your pace, time, and distance on runs. It's an especially exciting day when all your targets are met in green.