It's just there to compete with Samsung's "Galaxy Gear", I reckon.
I don't know much about either the Gear or the Apple Watch, but a mate of mine is a Samsung fanboy, and he loved his Gear when he got it - almost two years ago.
I'm guessing the Apple Watch does everything a FitBit does, too.
The problem with this line of thinking is the Gear's sales are pathetic. But hey - market penetration on the Diamond Rio and Archos Jukebox weren't particularly high, either. So either Apple has figured out some magical way to make the iWatch more awesomer than anything that has come before, or... I mean, "magic box the size of a cassette tape that holds all the music you own" kind of sells itself. "Display on your wrist that shows what's in your pocket" faces a more skeptical pathway.