The Chronos watch is based on a CC430 - an MSP430/radio microcontroller.
The pack also contains a CC1111 based USB dongle - an 8051/radio/usb microcontroller.
I've written a minimal operating system for the CC111x, which should be capable of running on this device (without USB support).
It's available here: http://code.google.com/p/pinkos/
(note - to get at the serial console, you'll have to do some fiddly soldering)
It should be possible to use the GirlTech IM-Me handset and dongle units to communicate with the Chronos watch, the IM-Me units both contain the CC1110 chip.
If