I think the fact that an average house will need so many is going to be the downfall of this concept.
It sounds like an interesting product. I can see some limited uses for it in the remodel/addition market.
I'm doing a master bedroom/master bath addition right now where protecting the landscaping, the stucco exterior, the terrazzo floors and the Venetian plaster walls in the existing structure takes precedence over everything else.
The current plan is to trench alongside the house and deliver a gas supply, a cold water supply, a waste stub and an electrical service for a new service panel. This is the route we chose because it's the least intrusive. An issue with the trenching is that home hosts some of the oldest Rhododendron and Azalea cultivars on the West Coast, so the trenching has been painstaking. Rhodie's and azalea's are also notorious for having massive root balls/ root mats.
Using this heater (current plans call for a Rinnai tankless) would eliminate the need for the gas service and make the trenching less invasive and less destructive on the landscaping.