Hi @ozsolt
I have a driver that turns a temperature sensor into a full featured thermostat.
I was using it all last winter as the main heating thermostat with the sonoff TH01 sensor (€20) and a zigbee switch (€18)
It has a greater precision in temperature changes (0.1ºc) than the thermostat I had (0.5ºc). I left the old Wifi thermostat as a backUp, 2ºc below this one and it worked perfectly all winter and I calculated it saved 10% on fuel over similar years in temps.