There's a lot of visualization and applications recently using brain waves.
One of the most popular ones was this one by Ariel Garten, CEO of Interaxon presented at LeWeb2010. You can watch her speech "Thought Controlled Computing" here:
Yes, we were sitting there in the audience watching her brain wave while she talks ;)
What about the Japanese usage of brain waves? There's a bunch of interesting installations, but I'll introduce a cute one here - "Necomimi" by Neurowear project. You wear cat's ear shaped device which would lay down if you are relaxed, stick up if you are concentrated.
Looks like I was concentrated when I tried it this time ;)
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