Aftermarket combustion air intake control

In an idle hot water furnace, it is well understood that the furnace itself presents a serious heat loss. Such is not related to combustion efficiency as the burner is OFF (which is often most of the time) --it draws warm air out of the building, heats it with the largest, hottest convection "radiator" in the system and vents it up the chimney.

My question:
Is there an aftermarket control that turns off the combustion air intake when the furnace is idle? I thought of designing one myself, but would prefer one that is tried and tested.

I first ran across such a system about 60 years ago--it was an oil burner manufactured by Timkin. In today's world, such are standard equipment on many or most new furnaces, but how does one retrofit an old furnace?