Awesome technology; the mapping of nervous system signals to computational tasks is becoming mature tech so I'm pretty sure the "10 year" timeline comment is a little pessimistic. And you won't need to shave your arm anymore than you need to shave your head to get Nia or the Emotiv Epoc to work.
And regarding Nia, other companies have matured the technology beyond where OCZ got with it (not to diss OCZ; I'm glad they released it): Check out the Emotiv Epoc. Emotiv's system doesn't require the same extensive training (though it does need some) and has more directional movement including some crazy crap like "rotate" and "disappear." I own one, so I can say it's not a magic bullet and will take time for the technology in general, and the Epoc in particular, to mature. But it does work, right out of the box.