Sarah Price from Google X sports the current model and shows the development history today at Google HQ. Here you see pioneer Thad Starner with the first prototype. It needed a backpack for the batteries. More below.
The display is up and to the right of the normal field of view. Looking into the screen is like looking up to see the rear-view mirror while driving. You can see a video feed from remote cam in Google+ Hangout. So you can use your Android phone to see around corners... or you could leave it somewhere (imagine teachers at the chalkboard - they really could have eyes on the back of their head). Explorer version will ship this year and the consumer version next year.
Sergey wants it to track emotional state in real time, so you can filter through the first-person photos and video captured all day to find the salient moments.
I thought they should include eye tracking for object selection for an augmented reality lookup. For example, you could send the face that you are looking at into Google Goggles to remember their name... and get a tag cloud from their social networks. When will they trademark Google BeerGoggles? =)