So the Rice team decided to investigate using sound instead of radio waves. Bone is known to be a great conductor of sound, but so far it has only been used to transmit analogue signals in applications such as checking how bone is healing after a fracture, and in hearing aids that transmit sound from outside the skull to the auditory nerve. To see if bone could transmit digital signals over longer distances - to a headset, say, from a sensor worn on the wrist - the team applied a small vibrator to various parts of the body. When they...