Each of Tenori-On's LED buttons can either be lightly strummed, sort of like a harp, or alternatively pressed down, whereby each button lights up. Musical notes are triggered by a regular line of light that moves from left to right, much like the sweeping line in PSP game Lumines.
Perhaps most interesting are the more game-like modes, where you can set off Breakout or Pong-style music balls that 'bounce' around the grid, triggering new sets of dynamics sound. These can be layered on top of the more traditional music making modes, creating what Iwai called, "a real musical instrument for our digital age, just like the Theremin was for the 20th Century."No idea when (or even if) it'll go to market, though Yamaha seem to have the rights to it.
That could have been an inspiration, though the Tenori-On appears to be a self-contained instrument, rather than an input device.
The theremin was hardly the definitive instrument of the 20th century - more like the electric guitar, then the sampler. How much actual music was written with one? Not much... I suppose he meant in terms of becoming some sort of an icon - but it's impossible to predict what's going to become an icon, and particularly foolhardy/questionable if you're responsible for the item in question.
Sortof like this then:
http://monome.org/pages/40h