SignalTrace “links devices that regularly travel together, correlating them to license plate.” It is a surveillance product that will sweep up and add all sorts of Bluetooth and other data to license plate readers, linking specific devices—and people—to cars.
Anybody who uses an Android phone and hasn’t dug into their Location Services settings, and hasn’t disabled them.
And anyone with iOS on default settings. For WiFi and Bluetooth, the default is that just hitting the toggle in the drawer thingy is “turn off until tomorrow”.