I've changed the firmware so that the holdoff interval is no longer restarted when there's an input pulse. Before, if you pulsed every 59 minutes, then the reset would never happen. The more I thought about that, the less I liked it.
Now if you pulse during the holdoff it won't do anything, but if did it every 59 minutes then every other one would still work.
In addition, just tying the line permanently to ground will reset the system once and never again. The input has to be successfully debounced to "off" before any attempt to turn it "on" will be recognized. And, again, the debounce interval is one second. The line has to stay either "on" or "off" for a full second before any change is recognized. And for "on," that state change is recognized exactly once and then it has to transition successfully to "off" before it can be recognized as "on" again (note that this description is of the input to the circuit - where "on" is shorted-to-ground and off is open).
That's about as robust a system as I can envision that doesn't involve sending commands or stuff like that.