I've been looking into augmented reality technologies lately; vision systems are getting really good. There are some good ones here (click twice to load Flash videos, or download AVIs):<p><a href="http://www.robots.ox.ac.uk/~bob/research/research_ptamm.html" rel="nofollow">http://www.robots.ox.ac.uk/~bob/research/research_ptamm.html</a>