I was sitting the office in the early days of the pandemic when my phone suddenly buzzed. "Allison's iPhone is trying to connect to your device." I rejected the request because I had no idea who Allison was. A minute later, I hear someone at the door. I was alone in the office, so I introduced myself, and asked if she had tried to connect to a Bluetooth device. She had not touched her phone at all.

This gave me an idea, I scanned for nearby Bluetooth devices while walking in the office. Turns out, there were lots of people in the building each thinking they were alone.

Just for fun, I set up a raspberry pi that constantly track Bluetooth near by and record their mac address. Every time a new device shows up, it pings me. And when they disappear it also tells me.

Everyone has Bluetooth turned on now because of wireless earbuds. You can easily track people like that.