Eye Tracking is a Hot Topic
The hottest post on
Reddit/Oculus/ today was a new article by
UploadVR about eye tracking.

Front of SMI tech demo on DK2.
Image credit: RoadtoVR
Watch this youtube video to see foveated rendering in action. Notice that part of the scene is focused where the user is looking, whereas the rest of the scene is rendered in less detail.
https://youtu.be/GKR8tM28NnQ