I agree, this is super cool. Really simple and elegant. For something along the same lines in IOS app form, I found UK developer Touch Press' The Orchestra does something similar but also mixes with a video feed of the Orchestra itself, and a running commentary http://www.touchpress.com/titles/orchestra/

You might of seen it in the Apple ads

it's $13.99, although to try something similar, I got Beethoven's 9th Symphony for free first http://www.touchpress.com/titles/beethovens9thsymphony/