I thought this phrase had to do with plastic surgery, but it is simply the combination of graphics and other information onto live video feeds. It has been used in movies, games and various industrial design applications for several years (this video from a few years ago is sort of interesting).
But now we're seeing this concept being pulled into cellphones. Add in GPS and location detection, and it becomes a helpful mapping application. This video is a little cheezy but explains the concept pretty well.