The UC-2000 built by Seiko went on sale about 24 years ago. It was called the "Wrist Information System" but looks like it was more of a wrist breaker to me. It received rave reviews back in it's day and can still be spotted on eBay selling for around the $500 price range.
The watch was Seiko's attempt to put a PC on your wrist. The controller acts as a docking station for the watch. You program the controller (the large part), dock the watch which then transfers the data between the two devices.
Via: SportsCounters