The third eye is the eye of wisdom. A Hindu and Buddhist concept, it refers to a consciousness/awareness that is beyond one's normal five senses. The fact that K.R.I.T. can sense his girl's third eye illustrates the strength of their connection.
In Gary Numan's "Cars," the message is that cars lead to a mechanical society devoid of personal interaction. This didn't stop automakers from using it in commercials. Both Nissan and Oldsmobile have used it in ads.