What else is there to do but create a mouse for your tongue? Valve employee and engineer Ben Krasnow has hacked together a mouse that can track your tongue. To accomplish this, Ben has detached the optical sensor of a mouse and elongated the connection via a ribbon cable. He then created a plastic mold that houses the sensor. In addition, to more accurately tracking your tongue, he has changed the red LED, that the sensor uses for tracking, to a green LED. This was done since the color of your tongue reflects green better than red.
While this tongue mouse isn’t as precise as using a finger, it is still practical to use it for a tiled, swipe-able, or even a basic yes/no interface.