I sat through a sales demo of a system similar to this a couple of weeks ago. I wound up asking him how it was even constitutional. He told me when he did the demo for the FBI and DHS the officers wanted to throw their phones into a lake and move into an off grid cabin. Shit is getting scary.
The system I saw used networked electronic devices to track you within inches. Lightbulbs, charging adapters, certain coffee pots, etc. anything that can draw enough power to emit a Bluetooth signal can be used.
My boss and I agreed we would never use the tech because they are going to get sued out the ass for using it. They are already using it in airports in Germany. They know everything about you by the time you pass the welcome mat.