Can water heater run while towing? Here's why . . .

gary, that would work, except this is a trailer -- no engine.

I am sort of surprised that no one makes an after-market kit that would accomplish what I am trying to do -- to run hot water into the fresh water tank, regulated by a thermostat. There must be a lot of folks who camp in cold weather -- everyone worries about freezing, right?

Gotta keep scheming here . . . there has to be a way to do this.