One of the reasons the Arduino is so successful is because of its flexibility - there's plenty of very complex ways you can implement the microprocessor board into a project - but that doesn't mean it can't do simple tasks just as well. Psycholinguist Franklin Chang used his Arduino to make a fetchingly homespun wristwatch.
Video overview of the Arduino watch after the cut
As well as showing multiple timezones - for instance LA and Japan in the image in the gallery below - the watch can also play Pong and Conway's Game of Life. The LCD is from a Nokia 3310 while the battery is a rechargeable lithium coin cell; the display and Arduino Pro Mini are both enclosed in the case that you'd normally keep your camera memory card in.
The knitted wristband is kept to the Arduino casing via bent paperclips, so hopefully Franklin won't be doing any strenuous exercise or jumping as it doesn't look the most stable of arrangements. More details on the Arduino Pro Mini here.