I think you're underestimating other here... I think there are lots of scenarios where a tiny start-up makes a barely functional and ugly HUD a good year or two before Apple comes out with those obnoxious sunglasses with glowing apples on them that we're going to have to deal with everyone walking around wearing from here to the Singularity (or at least from here to smart contact lenses). The technology is out there though not at all mature, it's mostly a software problem now.