How can we connect a smart thermostat to our heating system, which is a gas furnace and wood fireplace?
Do you get much heat flow out of the fireplace without the fan running?  Would it be possible to locate a Tstat to sense the heat from the fireplace?  I'm thinking of using a Tstat that supports air conditioning, but repurpose the A/C terminal and connect to the "fan on" terminal on the furnace. That way, when the Tstat detects warmth from the FP it would turn on "A/C" which is now actually just the blower on the furnace.   When the fire goes out and the house cools down, the Tstat would turn on the furnace normally. 

I'm not an HVAC guy, so take this with a grain or two of salt. You might need a pro to get this right. But it seems to me like an approach that might work.   Ed, Jack and Harper?  Ideas? Comments?