There are some really neat solutions for tracking things you may lose, like your keys. Solutions like Tile, Orbit, Trackr, and more generic ones are easy to find on the internet, but they all suffer from the same "problem" - they need your smart phone to find and report their location. This works well when you're out and about, but inside your home, unless you can hear the audible signal, you're stuck looking for it.
The ESP32-mqtt-room project began as a proof-of-concept to see if it would be possible to detect and report Bluetooth Low Energy advertisements to Home Assistant. While it is now deprecated and no longer supported, it served to show that using low cost microcontrollers, this is indeed possible. I am proud that the project succeeded, and has been forked 45 times as of writing, and lives on in the fantastic ESPresence project.