"Don't be discouraged if what you produce initially is something other people dismiss as a toy. In fact, that's a good sign. That's probably why everyone else has been overlooking the idea. The first microcomputers were dismissed as toys. And the first planes, and the first cars. At this point, when someone comes to us with something that users like but that we could envision forum trolls dismissing as a toy, it makes us especially likely to invest."
Do you know what the JoyBoard's designers went on to create, what they were trying to build all along?
The freaking Amiga.
Actually, that was a toy too. But it was a phenomenally cool toy that was vastly more powerful than a lot of people's work computers.
Just sayin
At the point that they are coming out of YC they would probably be tackling one small, seemingly non-consequential part of a larger problem.
Maybe they would explicitly state 'we are going to eventually revolutionize X' - but my bet would be they would fly under the radar for a while.
iCade Mobile, iControlPad, and the umpteen bluetooth ones that don't clip on, but connect wirelessly and give you a PROPER gamepad for your iPhone/iPad.
As for Android, you can connect PS3 controllers and any number of aftermarket ones like above.
I get that the above linked one works for both iOS and Android, but very few people own (and regularly game on) both types of phone at once, so needing a multi-platform controller seems like a pretty niche market.