It's a device you wear on your wrist, like a watch, that tracks your steps, heart rate, and other health things.

Personally, I think they're a little obsolete already, since anyone with an Apple iPhone has the health app built in, and it's more feature rich. The health app tracks your steps, and the barometer is even sensitive to sense how many flights of steps you've traversed (by sensing the relative air pressure from the top of a flight to the bottom). And you can track calories, and all sorts of other stuff. Most people already have their phones in their pockets, so it's been quietly collecting health data behind the scenes. Pretty cool to check out the graphs it produces.

Yea, it's not measuring heart rates, but it's doing pretty much everything else. I take my phone literally everywhere. It's never not in my left pocket, so my need for a fitbit is pretty minimal. You can always snag an apple watch, and that'll measure heart rate, and be infinitely more feature rich and capable than a fitbit (but also significantly more expensive).

I'm not knocking the fitbit, but I just don't think it does enough to justify buying one and wearing it all the time (for me, anyway). At the end of the day, it's different strokes for different folks.