Looks a bit bulky compared to the Coleman version:
Coleman - Hot Water Systems
I have one of these, and for a shower, it is almost perfect. Put the water pump in a bucket of cold water and you have a HOT shower. If you want nearly boiling hot water, put the output back into the bucket. When the water is almost boiling hot, then it shuts off.
I have heard that they don't last very long, but mine still works.