A free program for Android, by Florian Grill.

DroidJoy is an app where you can turn your Android smartphone into a real gamepad device to use on your games. DroidJoy supports many different game genres, such as action, adventure, and strategy. It also supports multiplayer games, so you can play with friends. The server can handle up to 4 clients, that way you can easily play with friends. The app is free to download and use.

DroidJoy is compatible with game platforms on Windows PC, and it is strictly not available on consoles. You can also play on a server that runs on your own PC as long as it’s Windows 7 or above.