rright,
We have several LaCross WiFi enabled weather stations in our greenhouse/chicken coop. Since the building also has a WiFi hotspot (doesn't every chicken coop have internet access:B), we can monitor the temperature and humidity via the internet anytime we want. Additionally, it's easy to set alerts so if the temperature or humidity exceeds a user adjustable set point, a SMS (text) message is sent to our cell phones. Have had the system in place for a couple years and so far it has worked pretty good. Occasionally (once every few months), we do need to reset the system but for $100 per station, it isn't too much of a pain. Just remember though that you will need a internet connection.
Alternatively (but not with the above system), you could have a dedicated cell line in the RV that would text you when the temperature exceeded a preset limit. I would think this option would be sort of expensive though in monthly fees.
Steve