Technical Illusions will supposedly have this for CastAR by using fairly new freeform optics techniques (AR/VR clip-on, don't think it has been demoed):
If it can deliver on the low-distortion, it has a major advantage over Oculus. The distortion correction for the Rift currently requires you draw to an intermediary render target about 1.5X the resolution of the screen. This throws away a lot of pixels and has a huge performance penalty, and the geometry-shader approaches to avoiding the penalty that were attempted so far haven't worked out.
http://technical-illusions.myshopify.com/collections/frontpa...
If it can deliver on the low-distortion, it has a major advantage over Oculus. The distortion correction for the Rift currently requires you draw to an intermediary render target about 1.5X the resolution of the screen. This throws away a lot of pixels and has a huge performance penalty, and the geometry-shader approaches to avoiding the penalty that were attempted so far haven't worked out.