Device online or offline?


Hello Community,

is there a way to find out if a device is on- or offline?

I have several rooms equipped with two temperature sensors (e.g. Hue motion sensor with temperature and NetAtmo) To the control my heating I use the average of both of them to feed a virtual thermostat. This works fine so far, but I had some problems with the heating when one of the two devices went offline. Due to the calculation of the average to control the heating, my thermostat receives a wrong temperature information.

Is it possible to check if a device is offline before using it for a calculation?