The Chronoduino uses an Atmega168PA microprocessor. On the peripheral side there is a DS1337 RTC, a BMP085 barometric/temperature sensor, and a MCP73831 Li-Po battery charging IC. Numerous headers as well as two buttons, LED, and a buzzer are on the board.
The idea behind the project is to design an Arduino watch platform (hence, quite unimaginatively – Chronoduino) that’s also usable as an ultra-miniature sensor node. Some parts are based off of Bazile Romain’s rev 3 MakerBot Watch, while some are completely new.
Via the forum.