My thermostat is high quality (two Herpstats by Spyder Electronics) at 15 years old and going strong), but it only turns off at a pre-set maximum temperature. I need an add-on that can "deliver" (not turn off) power for cooling when the temp hits a certain maximum. At that point the 'stat turns off. It would obviously need to be set at a higher temp than the "turn-off-at-the-preset temp" side of the thermostat. Otherwise they would both be running at the same time LOL!!
I can make a super-habitat to sell!.
Another device this tank would need is an anti-flooding mechanism. Two low voltage #20 bare copper wires held 1/64 inch apart will conduct electricity when they get wetted. We can already buy these switch-on-when-wet switches which are used on automatic skylights that close when the sensor gets wet from rain. Mine will run a 120V - 12 volt microswitch which turns on a cheap electrical 120 Volt water valve, and stop the mister, + stop the entire environmental controls cluster; the heaters, all lights, misters, etc., just to be safe. Luckily that one is easy to make and doesn't depend on the thermostat.
I can see it in my mind: The iguana poops on the flooding sensor and turns off all of it's equipment LOL!
The ambient temperatures here never get hot or cold enough to injure an iguana. But chronic exposure to these heat cycles will make an iguana get sick. So, here, the creature needs all those environmental controls.
I'm definitely looking into those low-wattage coolers.
I didn't think there could be any advice for this because I've never seen this discussed before.