Mobility

The Handheld Museum: A tribute to the early history of handheld gaming

Casio CA-90 -- The Geek Standard

Casio CA-90 (19xx, LCD, Watch Batteries, Model# CA-90)
Calculator watch that also features a game... From what I'm told, not a very exciting game though. I believe it's something along these lines: a number will scroll across the screen, and you have to press that number on the keypad.

** Any dork worth his/her salt had one of these.