I've been actually looking for bluetooth watches a while back. At least Ericsson makes them, but they are pricey and only work with Ericsson phones and WinMo devices that have a special program installed.

Otherwise it's a nice idea. I'd love to use the watch to skip tracks on my tablet and such a device could have potential of controlling who knows what as long as it has bluetooth.

Here are some things you can do with such a watch. I read somewhere that they communicate through COM port using AT commands, so it shouldn't be too hard to implement some of this stuff on tablets too!