The Joypad app turns your iPhone into a wireless controller for your PC or Mac.
To use Joypad you must install the app on your iPhone and a desktop client on your Mac or PC. Both devices have to be connected to the same WiFi network. The Joypad desktop client should automatically discover your iPhone is the app is running, but if not you can open settings and manually enter the MAC address of your phone which is given to you in the app.
As soon as the connect light turns green, you'll be able to use Joypad. The lite version comes with one 'pad, based on the old Nintendo Entertainment System. Upgrade and there are a number of more modern joypads you can use. Each button of the joypad can be configured to a corresponding key, and various configurations can be saved.
While touch joypads never quite match the real thing, Joypad is pretty good. Playing flash arcade games worked really well, as did playing old games through an emulator. As Joypad connects over WiFi, it is essential your connection is stable and not overloaded or it will suffer from lag. It's a shame bluetooth is not supported, as iPhones and Macs have it, as do many PC laptops.
Joypad is a great game controller app that's responsive and nicely configurable. If you hate playing with keyboard controls this could be just the thing for you - just hope no-one calls you mid-game!