It could be interesting but would take some careful testing work to be suitable for any program: most people don't hold their reading material completely flat; so it would have to have a very easy and functional way to recalibrate.and also be quite smart about handling shakes and sneezes and whatnot.

I think this, like 3D graphics, is one of those things that will build up to critical mass over time. It's never going to be a good way to navigate menus though lol.