This basically turns your PSP into a controller for your PC (running Windows). How it works is that PPJoy provides a way to create a virtual joystick. We can then communicate with this virtual joystick as though it were a real joystick. This is accomplished by running a server in Microsoft Windows. The server just runs in the background waiting for a connection. When you start the WiFiController program on your Sony PSP it will establish a network connection over wireless using infrastructure mode. Once it establishes a connection and obtains an IP address it will connect to the server running on your PC. Once it has connected to your PC it will act just like a regular joystick.This is an impressive mod, but I'm still waiting for the PSP homebrew that lets you flush your toilet... wirelessly.
[Via PSP Hacks]