No - I doubt most of us use one of these.
We just stick a heater in the van every night with the thermostat set at about 5 degress C. If the temps get colder than that then the heater comes on automatically without us having to give it a second thought.
If the temp don't drop that low, say because of cloud cover, then the heater won't come on. Simples.
We didn't heat the third van last winter, so we turned the water off from the tank to the pump, unscrewed and emptied the filter bowl and started the pump. This pushes the water out of it and also drains the pipe to the van's outside hose ports. The hose reel was brought inside. There was only one day when we had a block of ice in the tank and had to spend some time warming the hose to the tap to defrost it. The trip to work with the van's heating on wasn't long enough to warm the pipes enough.
I personally would see no benefit in having an alarm to wake me up to tell me it's cold in the van TBH.