Clickbait title in the OP, but they mean the methods coming out for tracking people without any electronic device on them at all via heavy filtering and pattern recognition to make 3D space snapshots due to the distortion in the WiFi transmission reflections.

What you are talking about are all surveillance devices based on compromising a specific device and using it to surveil an electronic device. The closest one of those device comes is the TAWDRYYARD which just communicates a position with light.

Though there is 0 doubt that this tech has been discovered and used by the NSA/mossad and other government intelligences already.