In the latest escalation of surveillance of travelers, data from automated license plate readers (APLRs) is being merged with data from devices that record the unique identifiers of passing WiFi, Bluetooth, and Bluetooth Low Energy (BLE) devices, including always-on devices intended for in-vehicle communications, entertainment, and network access.

Most new cars, SUVs, and light trucks have built-in WiFi access points and Bluetooth and/or BLE connectivity. Each of these wireless access points transmits a unique identifier — usually fixed or not readily changeable by the vehicle owner or operator — to enable devices in the vehicle — cellphones, wireless earbuds, etc. — to establish and maintain connections. Each of those devices broadcasts its own unique and often fixed identifier.

Once the unique identifying numbers of the in-vehicle wireless access points are linked to a vehicle and the vehicle's registration record and owner by matching the time and location of device detection with an ALPR scan of the vehicle's license plate, they can be used to track those devices and log their movements in a permanent file associated with the registered owner, even when those devices leave the vehicle.

So if you use your Bluetooth or BLE earbuds to listen to music or make a phone call in a car, even as a passenger, police can and possibly will continue to track your earbuds' movements and associate them with that car.

According to a report by Byron Tau for NOTUS  (a new nonprofit newsroom founded and funded by Robert Allbritton, the former publisher of POLITICO), wireless "device detectors" and the back-end systems to link ALPR and wireless device tracking data have been purchased by local police departments in border communities in Texas using grant money from the US Department of Homeland Security (DHS) and the  state of Texas.