I haven't used that one but we've had great luck with the Ecco Temp, which are about 150 bucks. I've installed three in the last year and the oldest one is about 7 years old and still going strong. I think the Camplux is the same thing.
Install it in a way such that it is vented to the outside, which is pretty easy to do really. And then plumb it into your hot water line and turn it up to max heat. Then if you have a mixing valve in your shower you can adjust the temperature inside just like you would at home.