Years ago, I read an article about a device the government created that allowed the user to talk to a person at a distance in a crowd. Only the person in the crowd would hear the talker holding the device.
Don’t you remember on ‘24’ Chloe was ALWAYS giving info to Jack thru an earpiece that allowed only him to hear?
We used to do that with a fire control radar dish, in-port with the power turned off. Just point the dish at a bunch of guys milling about on the pier a hundred or so yards away, whisper across the face of the dish, "get to work, maggots", or some such.
It would sound like a message from God himself.
That was late 1970s technology. Imagine what kind of stuff they have now.