I picked up a Zodi Hot Man Fire Coil on Friday from the local outdoors store. Apparently it was discontinued several years back and they didn't realize they had it.
Anyway, we used it over the weekend and it worked great. You just hook up two water jugs, or in our case a water jug and a solar shower. Place the jugs at different elevations, place the copper coil in the coals of the fire and turn on the water. It took us two passes throught the coil to heat it up to where we liked it.
Unfortunatly, after doing a search, I was not able to fine any additional information.