Has anyone seen this?

http://live.leapmotion.com/about/

Also, check this out:

http://mashable.com/2012/05/21/leap-motion/

I can't imagine holding my hands up for an entire work day.  I predict it will be a short-lived novelty item.  I think after a short time, a ";gesture"; of waving my hand and arm will add up to more effort than a scroll wheel on a mouse.  For graphic design, it won't catch on because it's not pressure sensitive like a Wacom tablet (also a big limitation of the iPad for artists.)  For everything else, keyboard shortcuts are faster/easier than what they show in their video.

Plug this bad boy into a SMARTBoard and you've really got something for classroom usage

I would imagine it's usability would depend on positioning; after all, the demonstrations had to be set up to be viewed video and don't necessarily reflect a real-world setup.  As far was usefulness, it would depend.  For graphic design it may be useful for creating frameworks and models, but not for digital coloring or painting.  For music?  Virtual keyboards would help save a lot of desk space... imagine an 88-key software-based piano!