There are plenty of smart thermostats that can save you money on your energy bill while keeping you comfortable. Looking for an open source version? The HestiaPi Touch is worth a look. It is a thermostat powered by a Raspberry Pi Zero W that comes with a 3.5″ touch display, WiFi, Bluetooth, and humidity/temperature/pressure sensors.
HestiaPi Touch has a 3D printed enclosure. It comes pre-installed with OpenHAB 2 and has mobile apps for Android, iOS, and other platforms. The thermostat can work with Google Home and Amazon Alexa. It supports most HVAC systems with five wires.[HT]