Augmented reality is just a vague term...
I could say my corrective glasses are an augmented reality device.
It is a vague term... but in essence it's no more no less than having a virtual overlay over the real world. Some phones with Cameras can already do that - to some extent - as a feature in some navigation and similar apps.
There are also already some location based games that use real map data and GPS to make you, for example, run away from virtual zombies in the real world... zombies which right now, you can only see by looking at your phone
If those Google glasses are a hit it may be another exploding market spawning all kinds of gadgets and games.