How about throwing in navigation data shown on vehicle windscreens? Of course, others would probably loathe this, but adverts shown on windows would also be another interesting way of implementing such technology. It seems that HP is not the only one looking into this seemingly niche market, as word has gone around that Samsung, too, is working on somewhat similar technology.
This patent is a long time in coming, especially when you consider the fact that it was filed all the way back in 2006, using light-reflective slats in order to display images which were produced by a computer on a transparent screen, simultaneously enabling light from behind the device to shine through. I suppose a consumer class device done right with such a display is going to be more than just a novelty piece.