It turns out that the tongue is the ideal interface through which to obtain additional information about the environment. 

U.S Navy Seals are currently in the exploration phase of testing a device that will help them "see" in soupy-water environments.  The plastic oral retainer device is connected to a infrared camera that transmits information to the tongue via 100 different microscopic metal points.  This seems to be enough information to be able to navigate successfully in a 3-D environment. 

Unlike every other part of the body the tongue has no dead layers of skin, the saliva conducts electricity well, requiring only 3% of the voltage of normal skin.  According to one prototype user, "it feels like pop rocks candy."