We use a 25ft PIRIT heated hose, controlled by a built in t-stat. I have felt the hose from time to time and have never, ever noted it to feel even remotely warm to the touch. It does work very well though as we just went through some pretty chilly -18*C nights with no problems / frozen water lines.
Cheers!
Mike
Something Old, Something New
2012 F350 SRW, 6.7l Powerstroke, 3.55's front and rear.
2008 Fleetwood Regal 325RKTS
Mike, Carol and our 4 legged "furry child" Kenzie Shweenie Tod