If I had a small trailer with some floor space I would consider something like these:
http://www.matsmatsmats.com/commercial- ... r-mat.html
http://www.allmats.com/site/439205/page/201168
It may work as a heater for some people's trailers. For some it may not work very well, but have a look.
I have heated floors in my bathroom at home and it's paradise on those cold winter mornings!