Another option is an IP Camera with a temperature sensor. Several companies make them. They allow you to monitor the temperature and watch video or look at pictures of your RV from anywhere there is wifi or cell phone internet coverage.
Simply put, you can set up a camera like the one below to send you a message when the temperature gets too high or if your dog barks etc. You could then watch a video or look at a picture if you want or even talk to your dog.
http://www.newegg.com/Product/Product.aspx?Item=N82E16881103072Note-I haven't used this camera so I can't confirm how well it works.
