Hygrometer
From Amazon
tado° Wireless Temperature Sensor - Wifi Add-On Product For Smart Radiator Thermostat - Digital Temperature Control For Active Heating Control - Easy DIY Installation - Save Energy and Heating Costs
ShopBetter24
Thermostat Tado V3P-WTS01-TC-ML White
Shopaide
Thermostat Tado V3P-WTS01-TC-ML White