Eye tracking have been around for quite a while and it seems that even normal cameras can track the eyes and eye focus (Tobii being world leader). If they use

Eye tracking have been around for quite a while and it seems that even normal cameras can track the eyes and eye focus (Tobii being world leader). If they use the technology mentioned here, it would be very high resolution (4K mentioned in the demo video) at a short distance (mm's) at full focus. But - just as you say, no one yet knows how Magic Leap reads the environment to do proper mapping and focusing on an object in real life (rather than on a screen like some VR headset do) should be very unpredictable.