This device is a wheelchair steering “wheel” in the form of a dental retainer instrumented with sensors that are activated by a tongue piercing. Georgia Institute of Technology engineers devised the Tongue Drive System prototype for people with high-level spinal cord injuries. From Wired UK:
The output signals from the sensors are wirelessly transmitted to an iPod Touch or iPhone. Software installed on the Apple device works out the relative position of the magnet with respect to the array of sensors in real time and interprets the user’s commands. This information is then used to control the movements of a cursor on the computer screen or to substitute for the joystick function in a powered wheelchair…
The system can be trained with multiple commands — unlike the common sip-n-puff device that acts as a switch controlled by sucking or blowing through a straw.
“Tongue Drive uses dental retainer and tongue piercing to control wheelchair” (Thanks, Ariel Waldman!)