Not my house but dang.

My lady sent me a link for a house since prices seemed to be coming down. This was one of the photos. Lets hear it...

 

Likely a L.P. heater?

 

I was worried about the pipe being so close to the wall...but I think you're right.

 

Those are gas furnaces that act like a fireplace, they operate way different than a normal forced air furnace. They are usually found in very small spaces, small houses... anywhere not very big, as there is no ductwork.
And yes, I have seen the chimney from them used as a radiant heater also. Such as the furnace being on the first floor in the front of the house, with chimney going up into the second floor and traveling to the back of the house and exiting there.