[izacus]

The way I solved this was by buying cheap weather stations from AliExpress. Many of them come with multiple temperature/humidity sensors powered by batteries - for as low as 70$ for a station with 4 sensors. Those sensors transmit on 433 MH or 838MHz radio which has excellent range (20m+ through walls) and long (months+) battery life.

On RPi side I only had to get an RTL-SDR receiver and run https://github.com/merbanan/rtl_433 on the RPi itself to decode the data.

It was significantly cheaper than going with BLE or WiFi sensors.

[cloudkj]

Just saw some of the references to RTL-SDR in the thread comments and started down the rabbit hole, and it looks like a fascinating area for hobbyists.

Can you provide some links to temperature sensors you've tried that work well with an RTL-SDR receiver? I'm also interested in setting something up with a Raspberry Pi.

[izacus]

The link to my original station which I used with SDR is sadly dead now, but I got one of these for 70$ now:

https://www.aliexpress.com/item/32810015137.html

(Hopefully the link still works.)

The sensors are kinda bulky, but still more reliable than anything I managed to build by myself :)