This project has been abandoned.
If you are looking for a way to build your own Smart Thermostat please visit our sibling project Smart-Thermostat.eu
In the case you already are using the Smart Thermostat for Arduino Yun, you have to know that the app will continue to work at least a couple of years, to facilitate the process of migrating to another thermostat.
The Smart Thermostat For Arduino Yun team, October 2019.