I think there are plenty of companies that try things out on the mobile OSs. Square-Enix released an entirely new IP (Chaos Rings) on iOS, and it's actually not that bad of a game. Unfortunately, I don't think they ever leveraged the A5 well enough, so it won't look remotely as good as the game could look.
GameLoft has also ripped off plenty of good IPs to make more console-like games on iOS and Android. The games are certainly large as I downloaded an update for Gangstar Rio that was ~900MB.
I'm actually a bit surprised that Apple hasn't tried to capitalize on the gaming market even more. I'd imagine that creating a small controller to go around the iPhone wouldn't be terribly hard to do. It could come in two pieces, you plug one piece (half of the controller) into the dock connector and plug the other half into the first half.
I think the only problem that you run into is that you can segment your market into a group of haves and have nots, which is usually a dangerous thing to do. It's the equivalent of why they don't let the PC gamers stomp all over those silly console FPS players.
I'm keeping my eye on a thread that I saw on Amazon about it.
The problem is that they charge too much for the same content. Plants vs. Zombies costs $6.99 for the iPad (higher resolution than the Vita), but the Vita costs $19.99? The PC version is only $9.99! It's even worse if you look at something like Dungeon Hunter Alliance, which is cheaper on the PSN for the PS3. Comparing the iOS version isn't fair since it is the same game story-wise, but doesn't include co-op (DH2 does).