Dasher, an intuitive

Apologies if this has been posted before:

'Dasher is a competitive text-entry system wherever a full-size
keyboard cannot be used, driven by natural continuous pointing
gestures'

Video demonstration
http://www.youtube.com/watch?v=0d6yIquOKQ0

More info and free download available at;
http://www.inference.phy.cam.ac.uk/dasher/

I think the use of a 'library of books' metaphor is truly inspired. - pauric