Some people on this board in the past had a temperature alarm in their RV that rang up their cell phone if the temp went over a certain setting. I am not sure of the brand name, but you can probably search and find it.
We have left our dogs in our class B with the generator going on moderate days, so we could attend a luncheon or some such thing. But that's with one of us running out to check every fifteen minutes or so. I would never leave them loose in the RV. Over the years, we've heard of some tragedies when dogs tried to see where their parents had gone and got into a deadly situation. Think of it like leaving a 2 year old child alone in the RV.