PadRacer is like Scalextric for the iPad, a top-down car-racing game for up to four players. The awesome twist is that those players use their iPhones to control the tiny on-screen cars.

The first game we know of to use this multimachine approach for the iPad is Scrabble, which lets players keep their tile-rack secreted on their iPhone screen and then flick the tiles onto the main board, over on the iPad, when it's time to play.

PadRacer instead turns the iPhone (or iPod Touch) into a wireless controller, connected via Bluetooth or Wi-Fi. You steer the cars by tilting the iPhone left or right.

The only caveat is that you can't play the game without an iPhone or iPod, so the audience is slightly self-limiting (and we wonder how many complaints there will be from people who don't read the warning first and buy the game without the right gear).

And we already know what you're thinking: The minimum price for the hardware to play a two-player game is $900 – one $500 iPad and two $200 iPod Touches. On the other hand, the game is just $5, and if you already have the hardware, then this could be a lot of fun.

Who knows where this stuff will lead? A first-person shooter with a sniper-rifle view on the iPhone screen? IPad Poker, with your cards hidden in the palm of your hand? Or even a Keynote remote on the iPhone, complete with preview of the next slide? One thing's for sure: The iPad is looking like a kick-ass gaming machine.

PadRacer [iTunes via Pocket Lint]