Has anybody worked with Optical Glyph Tracking or similar Augmented Reality techniques?

Here are some examples:
http://www.youtube.com/playlist?list=PL9237055E8D86D230
http://www.youtube.com/watch?v=pnDZsXK1X9Y

If you have, have you used the Metaio SDK? If so, what do you think about it?