http://www.technovelgy.com/ct/Scienc...p?NewsNum=1256
"The Pantech phone uses bone conduction; when the phone is placed against your jaw, the mechanical vibration from the phone is conducted to your inner ear, which responds normally. The result: you hear the other person on the phone perfectly."
Key advantage: it makes it easier to hear phone conversations in a noisy room. The sound is conducted directly to the inner ear.