If you like to play classic video games using emulators on your PC or Mac, this is the app for you. Joypad is an app that lets you use your iPod touch or iPhone as a classic joystick controller for game emulators on your Mac and windows PC. You just need to download the app from the app store and the connect software for your Mac or PC and you are good to go. The software works with Wi-Fi, Bluetooth as well as ad-hoc connections. It has a two-button and a six-button layout which supports a variety of games.
The app is free to download and comes with Game Boy Advance, NES, SNES, Genesis and N64 gamepad skins. You can also buy additional skins for $0.99 each, including Game Boy, Game Boy Advanced and others. Current iOS games supported by the program include Stardash, Arcade Jumper, Meganoid, Super Drill Panic, Ghost Ninja: Zombie Beatdown, Ninja USA, Lars, Vertex Blaster, Super Mega Worm, Plum Crazy, Emerald Mine and Space Falcon Reloaded Free.
For Developers there is this Joypad SDK that allows them to enable their iOS games to work with this app.
Here is a Video of Joypad in action.
Download Joypad for free.