I adopted ST a few weeks ago and I have just written my first app. There may be other apps that do something similar, but I came across a post on Reddit where someone was looking for something like this so I figured it would be a good learning experience as I plan to write more code.
Basically the app accepts a bunch of devices capable of measuring temperature. Based on the average temperature of the selected devices you can set your thermostat to cool or heat (and specific temperatures). I don’t have 2 thermostats but I believe if you install the app twice it will work just fine.