I have one of these, but I have not used it other than a quick test. The
> top gets quite hot, and it's not for inside use. Also, the flow has to be
> pretty slow in order for the water to stay hot. The 2 D cells just power the
> sparker, which kicks in when you turn on the water, until it's lit...
>
For what it's worth, I have been using the Coleman hot water on demand hooked up to a Eurovan style faucet with a dishwasher quick connect. I turn the water on from the Westy faucet, then the Coleman, and within five seconds I have steaming hot water. The hose could easily be routed out the window for a shower, although I generally just use the Coleman indoors for dishes (with proper ventilation of course) Much faster than the Westy stove. The Coleman can also be hooked up to a 5 gallon collapsible bag or the pump can be put directly into a stream.
I like the fact the Coleman has its own power source for the pump. You can get nearly 30 minutes of hot water on one charge, which is pretty amazing.  A cigarette lighter adapter can than bring it back up to charge while in route.

This other device appears to have similar capabilities, (less the pump) although not everything is included. I'm sure it could be hooked up the the westy H20 tank too. Please let us know how your system works out when you gain more experience with it. I do like the fact this other device seems a bit smaller. The Coleman takes up a fair amount of space, but it also has its own built-in pump  propane source, and pwr source.

Technology sure has changed the way we do camping! Years ago, a solar powered shower was about it. Ain't life grand?

Troy