People with high-level spinal cord injuries have been incredibly limited in the available options for mobility.  The Georgia Institute of Technology is doing something about that.  It's on the tip of their tongue.

The sip-n-puff device most commonly used allows for only two movement commands.  This is very limiting in a three dimensional world.

Electrical engineers at the Georgia Institute of Technology have demonstrated proof-of-concept on a device that allows for wheelchair control using the tongue and a dental appliance.

The tongue in pierced and a magnet stud is inserted.  The patient then dons a dental retainer that has sensors embedded to determine where the magnet is on the sensor.  This information is transferred wirelessly to an iPod Touch or iPhone.  The information is then sent to the wheelchair, much like a joystick sends commands.  It's called the "Tongue Drive".

Originally it was devised with a head worn contraption.  It would become dislodged easily and need frequent recalibration.  Thanks to Steve Jobs, a magnet and some custom grill work, easier to control wheelchairs for patients with high level spinal injuries is a near reality.

For more see this source article.