Google are currently working on some glasses that have a HUD (Heads Up Display) a bit like the one in terminator and are rumored to look like the Oakley MP3 thumps :
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They are based on old Android smart phone technologies and might have specs similar to these 1GHz ARM A8, 256MB RAM and 8GB of storage.
The navigation system currently used is a head tilting to scroll and click apparently it is very quick to learn and once the user is adept at navigation it becomes second nature and almost indistinguishable to outside users.
The HUD is only going to be in one lens (don't know if it is left, right or user defined yet).
They will probably be released on a public beta test soon