Home Automation

I'm looking for a thermostat setup that will only turn on the heat below a certain outdoor temperature. My current wiring is a 2 wire setup to a gas furnace. Currently controlled by a simple Honeywell programmable thermostat. I previously used a Nest Thermostat E (which I hated). I'd prefer not to rewire the furnace if possible.

Now the background.... This spring mini splits were installed around the house mainly for AC in the summer months, but heating as well when it is more efficient during the spring and fall. The gas furnace was kept as heating for when the temperatures drop. The area I am in can get really cold (-20f) so keeping a backup heat source was a necessity, but most of the time in the winter is warmer than that. Ideally, I'd like to utilize the mini splits for heating when it is above 20-30f (don't know the exact cutoff yet) and only use the gas furnace when the temperatures dip below that. The mini splits (2 separate units) are not connected to the central thermostat.

Instead of doing this manually, turning everything on and off, and checking the weather constantly, I'd prefer to have a thermostat/weather station that reads the outdoor temp, sends that to a thermostat, and then runs the gas furnace below that temp. When it is warmer, it never runs. I can't seem to find an auxiliary heat only thermostat that does this. The only smart thermostat that I've found so far that could link this is an ecobee with a weather station feeding it, but would require rewiring my furnace. Are there any options for this with a 2 wire furnace?