I had some issues as well, but recent updated thermostat adapters seem to have fixed them.
Nonetheless, I had the setpoints jump to crazy levels like 220, or really low like you suggested. Fortunately I was in town, so no REAL damage. (Other than my wife waking me up because the house was freezing, and setting back the acceptance of Insteon a few months...).
I set up a couple of triggers for when the setpoints pass bounds of reasonability. Outside of where I'd ever set them, and wide enough that they should never interfere with normal operation, but still narrow enough to prevent damage. If setpoints ever move above 85 or below 65, then an action setting them back to 75 or something triggers (and triggers again after a 1 minute delay, just to make sure the message gets sent). Also, send me an alert so I would know it happened. The triggers definitely saved me a few times, but then I got the revised thermostat adapers. Zero troubles since.
Take a look at The Thermostat Enhancement Plugin, at http://www.schollnick.net/wordpress/hom ... at-add-on/
It already will warn you via email if your house temperature exceeds or is below the configured temperatures.... I believe it would be an easy addition to add an override, that will not allow the temperature to be set beyond a certain value....
But, here's a question....
Currently the Thermostat Add-on, asks for:
(I'll need to change that to add Warning Emails as a header)
But would you like a checkbox for:
Only allow Temperatures within the Warning Temperatures
Do you think that would be usable to you?