I had same thoughts, but these type RV furnaces draw several amps through the stat.  On a home unit, you have a relay.  Also, home systems are for 24 volts AC not 12 volts DC.  If you always were on 110 you could get a cheap digital stat, a 110v to 24v transformer and a relay and make it work, BUT I assume since you are using gas heat, you don't have 110v.  The bigest problem is the location of the stat.  Heat rises and the stat should be about eye level, like in your house. I did re do one in a pop up camper with  a long cord and velcro and you mounted it after you set up.  Worked much better.