A neckband that translates thought into speech by picking up nerve signals has been used to demonstrate a "voiceless" phone call for the first time.Nerve-tapping neckband allows 'telepathic' chat (New Scientist, 12 March 2008)
With careful training a person can send nerve signals to their vocal cords without making a sound. These signals are picked up by the neckband and relayed wirelessly to a computer that converts them into words spoken by a computerised voice.
And here's the demo:
H/t: Marc Andreesen