“Beacons” are a highly marketed socially acceptable thing in the advertising industry that has permeated the insides of most buildings.

Standing too long in one aisle lets them know where you like to browse in the grocery store.

When they first rolled these out in the US at least a decade ago I used to get notifications all the time.

Stuff like “Near Well’s Fargo? Balance your checkbook.” As notifications.

Probably, it's how bluetooth is used to track devices/people too.

Nah. That's standard BLE protocol.

BLE is actually pretty secure, but it does advertise, and some folks take advantage of that.

it's certainly a good reason to not carry a bluetooth device if you're trying to do something in secret