I have written a Linux driver for the watchdog found on the MSI Fuzzy CX700 mini-itx boards. The watchdog is a feature of the superIO chip from winbond called w83697ug.
The CX700 manual contains example assembler which looks as though it was cribbed from the w83697ug datasheet, I used those two manuals to adapt an existing watchdog driver to the new chip.
The manual for the CX700 board is not easy to locate, so I have taken the liberty to mirror it here: msi-f700-E_9802v1.0.pdf.gz [4.8M]
Anyway enough rambling, the patch is here: winbond-w83697ug-watchdog-linux-188.8.131.52.patch.gz [12K].
Update 2008/11/26: It seems the patch was merged into 2.6.28-rc1, so from 2.6.28 I will not have to patch my router kernels, yay!
The full story is on the dedicated page, the patch is a simple one-liner that adds the device id to the existing cp2101 driver.