Meet the Sensor Watch: a classic Casio watch upgraded with a ARM Cortex M0+ microcontroller that is ready to be hacked. It uses Casio F-91W’s monochrome segment LCD instead of a high-resolution TFT LCD. This watch comes with WiFi and Bluetooth connectivity. It runs for a year on a 100mAh coin cell.
The Sensor Watch can display the temperature, time, one-time passwords, and a whole lot more. Its sensor board is modular and swappable. This is an open source watch. You can find out more about it here.