Yep, they are called donkeys. Mate of mine made one years ago when he was living in a caravan in the bush while building a house. Never did see how he did it but a house of five used it for six months.
Some National Parks in Queenslad have installed them.
Do a search for "hot water donkey" on Google.
Below photo is one at Crows Nest National Park near Toowoomba. You light the fire underneath, wait for it to get hot, turn the tap on and hot water pours out the other side.