Disney researchers have developed a microphone that lets a user record a voice message and then relay that message to another person simply by touching them with a finger. The microphone converts the voice message into an inaudible signal which is transmitted to the body of the person holding the microphone.
It can then be transmitted from that person's body to another person's body through touch. The recorded sound only becomes audible when touching someone else's ear. The sound can't be heard by anyone else but the person being touched. Look at a video of this concept.