Other than current on/off state you'd have to "decode" the data being sent to the display.
I'm with everybody else. It's easier to start-over with a temperature sensor (and some other stuff) or buy a WI-Fi thermostat.
It's usually the same with programming... It's often easier to start from scratch and write your own code than to figure-out someone else's code and modify it to your needs.
Or if you are doing home automation there are thermostats that use one of the home automation protocols instead of Wi-Fi.