Back in the 90’s it was revealed that cable television services could detect people in the room and this was technology developed for Neilson ratings collection; the technology could match family members registered with Neilson ratings collection with the programing they actually watched.
And about 10 years ago there was an uproar because a top level meeting in Tibet re Dali Lama was infiltrated by china remotely activating the microphones on laptops being used in a meeting. No indication to user given (no indicator light etc.)
The Clipper chip was a chipset that was developed and promoted by the United States National Security Agency[1] (NSA) as an encryption device that secured voice and data messages."[2], with a built-in backdoor. It was intended to be adopted by telecommunications companies for voice transmission. It could not only encode messages but decode them as well. It was part of a Clinton Administration program to allow Federal, State, and local law enforcement officials the ability to decode intercepted voice and data transmissions."[2] Each clipper chip ha[d] a unique serial number and a secret unit key, programmed into the chip when manufactured."[2] This way, each device was meant to be different from the next.