Quantity   Component name
2 × NodeMcu ESP2866 ESP-12E Micro controller with WiFi module built-in
2 × BMP280/BME280 I2C/SPI Temperature, humidity and atmospheric pressure sensor
2 × Breadboard Electronic Components / Misc. Electronic Components
1 × Software: MQTT Dash for Android. Nice app to check everything is feeding the broker, the status of the boiler and force the boiler ON if wanted
1 × OpenHab An easy way to get a control panel
1 × Raspberry Pi To act as MQTT broker and do the logic to turn on/off the boiler.