I purchased an Eccotemp as a stop gap to repairing my tank water heater in the motorhome. I found it SO wondeful that I didn't bother with the waterheater repair. I hung it on the wall in my shower and simply moved the flex hose from the tap to the Eccotemp, used a portable propane bottle and was happy as a clam.
Like anything propane, using indoors is a matter of caution for sure. The Eccotemp vents out the top, however, I used it inside with no ill effects. It was only on long enough for a shower.
I intend to install it in my Kit, wall mounted near a window in what is now a temporary bathroom.
I would NOT bury it behind walls or in a chamber, but I do feel that using it hanging in a ventilated area is perfectly safe.
It weighs almost nothing as well, I suspect a major advantage is there for those wishing to find ways to cut
weight.