this type of devices have been available for a while... for those who fly on a regular basis, you could not miss these in the SkyMall magazines all over the planes.
the natural focal length of the eye lens is something around 20 cm, so anything that is projected to appear farther that that does not require accommodation. The eye lens is not strained anymore.
I guess these devices use divergent lenses to form the virtual image at a distance greater than that.
I'm waiting for the 3D application of these, would be kinda cool to watch a movie from a memory card on your glasses in 3D. Of course, the tech is not there yet, but in time...