It works!

I checked in the watchdog script into the firmware repository. It now uses syslog rather than standard out/err for some rudimentary logging. My recommendation is that you run this from cron every 4-6 hours. You can't really run it more than hourly, since there's a one hour hold-off in the firmware that is reset if you try to do the reset before the hour is elapsed (so if you pulse the action pin every 59 minutes, it will never actually work after the first time).

The reason you don't want to run it more frequently is that if everything goes terribly wrong and it's doing something crazy, you want to have a chance to get in and stop it. The one-hour firmware hold-off should give you a chance even if everything else goes sour.

The only thing left would be to make a 3D printed case for it, but I don't know if I care that much. We'll see.