I have a few that sit around the house. Most of them are simple digital thermometer/hygrometer doodads. I use them in areas I'm working where the heat is turned off, to make sure it doesn't get too cold. If it does I wheel in an electric space heater.
The thermostat for the heating also shows the temperature, as do the control boxes for the HVAC. The software to control the HVAC from my phone also shows the temperatures.