4$ Xiaomi thermometer custom firmware LYWSD03MMC BLE TLSR8251

Repos :

https://github.com/atc1441/ATC_MiThermometer

https://atc1441.github.io/TelinkFlasher.html

I have been looking for a low cost, programable thermometer now for several years. A a handful of bucks? Wow. Just ordered a bucket of them from AliExpress - fantastic stuff!