Wikipedia
The Ruputer was a wristwatch computer developed in 1998 by Seiko. In the US, it was later marketed as the OnHand PC by Matsucom.
The Ruputer had a 16-bit, 3.6 MHz processor and 2 MB of non-volatile storage memory and 128 KB of RAM. Its display was a 102×64 pixel monochrome LCD. Its main forms of input were a tiny 8-direction joystick and 6 function buttons. It also had a serial interface and an IR port for communicating with other devices. The main body of the device (separate from the strap) was roughly 2 inches wide, 1 1/8 inches across, and 5/8 of an inch deep. It was powered by 2 high-powered watch batteries, which supplied the device enough energy for approximately 30 hours of use. Under normal conditions, the watch powered down when not in use in order to extend its battery life. The device was distributed with a SDK, which allowed for creation of new software written in the programming language C.