Quoted from Dayhuff:
What's a Fitbit ?
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.