Happy Bubbles Bluetooth Receiver
https://www.happybubbles.tech/presence/detector
What is it?
Each Happy Bubbles presence detector listens for Bluetooth low energy advertisements around it that are sent constantly by things like iBeacons, or even your phone if you make it act as a beacon. The detector also connects to your home WiFi and an MQTT server of your choice. Each detector will then send the beacon advertisments it sees, as well as their signal strengths, to the MQTT server over WiFi. You can subscribe to these topics through your MQTT broker.