We bring our dogs along many places and we do at times leave them in the RV with the AC on. (For folks saying leave them at home, what do you think fulltimers, camp hosts, etc. do?) Of course if there are campground rules against it we don't, but the vast majority we've been to that are dog friendly just don't allow them to be unattended outside.
Our two boys are labs and are crate trained at home and the RV is no exception. We don't leave them unless they've had plenty of walking/hiking/playing to ensure that they'll be napping while we're away and we always close the shades for them. One of our guys even will go in his crate when he's tired to signal us to leave. Our rule of thumb is to not be away over 4 hours when we're at a site with hookups. We've used the genny to run the AC during a stop at a restaurant or museum or something for about an hour. And a couple of times we've been dry camping where we leave the windows open and the fans on, but that's been in the cooler spring or fall...and in those instances we've just gone to the swimming beach for a quick dip or something.
All that said, we are always entirely prepared for one of us to stay behind with the dogs if they are not totally relaxed and comfortable. Now that they're both adults we don't ever have to, but we're ready to do it if need be. When one was young we took turns staying back a few times (oddly enough, that's the big lazy one that now kicks us out!)
We also use our phones for temperature and power monitoring. If you have an Android with built in temperature sensors (our Samsung Galaxy S4's do) it is an easy setup. There's an app called Temperature Surveillance and you set one phone up with whatever temperature thresholds you want and give it a cell number to text if the temp goes above or below your thresholds or if the power goes out. I think there are aftermarket add-on temperature sensors that you can plug into your smart phone as well.
I think it comes down to being aware of your dog(s) and their temperament and easing into the lifestyle. We certainly didn't leave either one of our guys for 4 hours off the bat. We started with making sure they were comfortable in the RV in general for a few trips, then being away for 5 minutes with us within ear shot, then 10, 15...you get the drift.
Oh, and we also have a sticker on the entry door letting people know there are two dogs inside and please rescue in case of emergency. Not sure if it would really help in a true emergency, but worth having on there. I also think it probably would make a would-be thief think twice.
