Technology

From my home office, running Bluehood in passive mode (just listening, never connecting), I could detect:

• When delivery vehicles arrived, and whether it was the same driver each time
• The daily patterns of my neighbours based on their phones and wearables
• Which devices consistently appeared together (someone’s phone and smartwatch, for instance)
• The exact times certain people were home, at work, or elsewhere

I mean, forget just locally monitoring around you. Google and Apple's Location Services, used by iOS and Android devices, phone home with the MAC addresses and signal strengths of nearby Bluetooth devices, so they know when all those devices were active and where. Unless it makes use of MAC randomization, they can track it. You can identify a device's manufacturer by its OUI, the first 24 bits of the MAC.

Google knows where people with Bluetooth headphones have gone, even if those people have never used Google products, just as long as they've been near someone with an Android phone using Location Services. They can probably identify where many people have met each other, by correlating locations of devices. They know, say, when and where Bluetooth-enabled Lovense sex toys were active.

https://www.youtube.com/watch?v=IRELLH86Edo