Ima have to call BS on the actual X-ray theory. Like Clark said, our vision is based on light. Our eyes receive information about our surroundings, not send anything out. An X-ray machine works because it sends out x-rays that can penetrate an object. So unless our eyes adapted to be able to pick up on seeing these xrays, or we implanted something in our eyes that let us project xrays, there really isnt any way I could see this becoming fact. At least not in the way that we can just stroll around and see through things.