Whispering is outdated. Disney Research has come up with a cooler idea. You turn your secret signals and transmit them by touch!

The Ishin-Den-Shin installation—named for a Japanese term meaning "telepathy" and/or "tacit understanding"—it takes the sound spoken out of a microphone and reconfigures it into high voltage, low current, inaudible signals beamed into your body and sends it out as soon as you touch another person's ear with your fingertips.

The inaudible signal vibrates the listener's earlobe and works as a tiny speaker to deliver the message. How cool is that. Inventor Ivan Poupyrev of Disney Research in Pittsburgh, Pennsylvania described it to New Scientist:
If you remember the beginning of The Hitchhiker's Guide to Galaxy, when the Vogons arrive to blow up the Earth, they turn every object on Earth into a perfect hi-fi PA system that is used to announce that the Earth is going to be destroyed. Ishin-Denshin is something along those lines, minus destruction of the Earth.

[Disney Research via New Scientist]