Don't use it for RV, but several years ago I bought http://www.radiothermostat.com/ and can monitor, or adjust the settings from anwyhere in the World as long as I have internet connection.
Would assume that on campgrounds you have WI-FI and if not, you can have cellphone modem, or tethering.
Synchronizing the thermostat with WI-FI is a bit of a headache, but later you can check the indoor temperature from your smart phone or any computer with Internet.
I think latest option was a monitoring camera that can be attached.
Those thermostats sell at Home Depot for less than $100 and I bought one on manager's special for $45.
Looks like not much demand.