The above video shows an example of how Audeo from Ambient Corporation allows you to communicate by moving your mouth while not producing any sound
Just when you thought you needed to use your voice to speak, along comes Audeo, a neckband which uses the signals between your brain and vocal cords to translate your mouth movement into information a computer can understand. From there, "speech recognition" can be used to convert these signals into words.
This works whether you speak or not. People could converse with one another using text to speech and not making any sound themselves. In other words you could instant message others by just moving your mouth and not making any noise or using a keyboard.
It will be interesting to see how this technology progresses. Initially it targets people who have diseases impairing their speech and I would imagine the business market would be next.