Using the Wyze climate sensor, I created a rule to turn a Wyze plug ON when the temperature is below 69 degrees, and another rule to turn the Wyze plug OFF when the temperature is above 70 degrees. A normally open isolation relay (Digital Loggers AC Sense Relay for $16.95 on Amazon) is plugged into the Wyze plug. The normally open contacts are connected to the two (2) thermostat wires for the selected heating zone. No C wire is needed.
The Wyze climate sensor is placed in one room of the selected heating zone near the existing thermostat. The Wyze plug and isolation relay are connected to the two thermostat wires for the selected heating zone in the boiler room. Alternatively, they could be connected at the existing thermostat for the selected heating zone. The use of an isolation relay assures that no stray voltage leaks onto the thermostat wires. Note that the Wyze Climate Sensor requires the Wyze Sense Hub.
Using the Wyze App, I can remotely change the temperatures in the rules to effectively control the temperature setting of the improvised thermostat.
As a fail safe, I also left my old manual thermostat in place and connected to the two thermostat wires. By setting the old thermostat 60 degrees, if the improvised thermostat fails for any reason, the manual thermostat assures that the temperature will not fall below 60 degrees.