Makes you wonder why someone doesn't sell an inexpensive, flexible heat exchanger.

Maybe a radiator with a small electrical fan that goes on the inside of the house, connected to a coil and circulated with a small electric pump.

Just put the coil in your choice of heat; wood fire, charcoal fire, propane BBQ, small alcohol burner, etc. and turn on the pump.

Extra credit uses a user placeable solar cell and battery set to keep the motor(s) going.

A small version of this could be used for vehicle heating.

-john