Most everybody who hears about rocket stoves wants to make hot water with one... the detriment to this, is waters ability to go from a liquid to a gas in a millisecond (well maybe a real second )the result is an ugly occurrence known as BOOM / SQUISH bad deal and you don't want to experience it.
I search quite awhile to find an old video that I would like to share. Geoff Laughton in Australia has built a safe, stand alone rocket stove water heater! Here it is
The system was commissioned last winter and it works very well. It's an open vented system that is connected to a standard oil fired CH system via a 'neutraliser'. It provides hot water for heating radiators and domestic use.
When I get time I'll post an article on its construction and operation on the forums.