I wouldn't mind a Bluetooth watch, that would be cool
But I don't see much use for anything else...if it's an extra item for me to get out of my pocket then I would rather just get out the PPC.
However, I like Trimac's idea of a BT all in one device including a mouse, simply the only reason for me would be games - for everything else touch screen is fine (in fact better than a mouse IMO).