Zak Kemble wrote a post on his blog detailing his digital wristwatch with a 1.3″ 128×64 OLED display, AVR ATmega328P microcontroller:
The main incentive behind this project was to see how much I could cram, in terms of both hardware and software, into a wristwatch-like device that is no larger than the display itself. An OLED display was chosen for being only 1.5mm thick and not requiring a backlight (each pixel produces its own light), but mostly because they look cool. The watch was originally going to have a 0.96″ display, but this proved too difficult to get all the things I wanted underneath it. Going up a size to 1.3″ was perfect.
Check out the video after the break.