The good: Comfortable, Sleek design, Long battery life, Automatically tracks exercise, Swim-proof The bad: Lack of a screen limits its usefulness Who should buy: Swimmers; Those looking for an inconspicuous fitness tracker and don’t necessarily care about seeing fitness data in real time. Fitbit’s fitness trackers have become more complex and sophisticated over the years, with some of the company’s wearables even offering a digital fitness coach or built-in GPS functionality.