Wouldn't the temp range be about the same for the MT and the HLT? Doesn't the device need some kind of electrical supply? Don't tell me they need you to put a battery in it right next to a burning propane tank!
Gas stoves use thermocoupler without electricity. They maintain temp at whatever you set.
I like the idea of a temp controller for HLT, I'm getting a new burner and kettle soon, so I'll use existing settup for HLT. Let me know if you get the unit how it works.
I had one for a little while. It is purely a thermo-mechanical device and does not need electric to work. Bottom end temp was 200*F so, it was useless for brewing.