This is what I had been trying to do and I made it.
If you ever wanna give it a try , use your PC to control a RC Toy , this can be a good example for you.
So , the target is : Use a PC to control a RC Car
My example is , I wrote a program which can handle the gamepad windows event then send the signal to Arduino. Then Arduino generates appropriate voltage to control the Radio Controller of a RC Car.
Feel free to have a look and let me know how do you think. https://sites.google.com/site/arduinorccar/