Yeh. Tongue texting while driving is not advisable although I gotta say that using a harmonica holder is a clever idea.
Here's a patent for a wearable tongue-keyboard:
http://www.faqs.org/patents/app/20110032126
There are a number of ongoing efforts to develop a true tongue-computer interface for the disabled. Some use a capacitive touchpad attached to the upper palate like a denture; others track a magnet imbedded in the (ahem) tip of the tongue.

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