[Hi! Google brought me here.]

I must be missing something -- what is the sensor connected to?  Is that switch a smart switch with available GPIO pins or something?  What is actually reading the sensor and sending the data to the smart home system?

Many thanks for reply. I'l try them in the switch then. I thought hot air rises up so sensors in the ceiling (incorporated in PIR) would have made more sense with more accurate reading.

Yep seems to be.  I bought some little digital room temp sensors, and balanced them on top of the light switch & compare readings.  They are within +/- 0.3 or 0.4 of a degree- although I think the digital sensor I bought is not very accurate.  I was told by a home automation specialist that the light switch is the best place, as room temperatures vary from the floor to the ceiling, and our perceived temperature at light switch height is the best.

It maybe that they are slightly slower to respond to temp changes behind the light switch, but only by a factor of minutes- not hours.

Does it pick up reliable temp reading given tucked in behind the switch in the wall? Thanks