TechCrunch has an article about a startup called iMo, which aims to enable control of any PC game using an iPhone or iPod Touch. The idea is to reduce the need for gaming peripherals while you're on the move, and make motion-control available to more players. Quoting:
"The system also features onscreen controls for the iPhone and iPod Touch, as not every PC game will benefit from using things like the accelerometer, obviously. This all works via both Bluetooth and WiFi connections between your device and your computer. The plan is to offer iMo in the App Store for $0.99; the first version should be available new in the App Store. And long-term, the company hopes to make it available on other mobile platforms as well, including Android. And ultimately, they'd love to include support for gaming consoles as well, like the aforementioned Wii, the PS3, and the Xbox 360."