Like Fitbit's Alta and Charge 2 ($149.95 at Fitbit) (Opens in a new window), the Flex 2 is essentially a tiny, rectangular module you can swap between various wearable accessories. It's a great entry-level tracker, though the Misfit Ray puts up a tough fight in the style department. The Flex 2 is slim and modular, so you can place the tracker portion in a variety of different bands and bangles. Instead of a display, there's a row of colorful lights that blink to indicate your progress and alert you of phone notifications. There's no built-in GPS or heart rate monitoring, but that's no surprise at this price point. It automatically tracks swimming, along with other activities like biking, running, and walking.

The Flex 2 ($99.95) is Fitbit's first fully waterproof fitness tracker, as well as its slimmest.

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