Found this while browsing around
Westfalia Water Heater & Shower
Seems like a nice idea... and quoting:
"From a cold-engine start it took only 30 minutes for the half-full water tank to reach just over 55oC! From a hot-engine start it took only 15 minutes to heat the half tank of water."

Seems an interesting and smart mod to a car's cooling system... perhaps...

J

many boats use the same heat exchanger/calorifer principle off the engine to heat a hot water tank. It works very well and can produce loads of very hot water.