With very little work you could implement a low cost open-source controller using Arduino.
Swerve Bot with low-cost Arduino controller
Everything you need to get this system up and running is available off the shelf...and we have the code to get you going with wifi if you don't want to write it up yourself.
One obvious drawback to this approach is that it doesn't give you any practice with the actual comp hardware. Still cool and cheap.
See here for documentation on the previous iterations of this project...
IPGamePad open-source code