(sorry for windows users but it is quite the same)
Then you can find some algorithm which can detect your face or some couloured shape. (search Haar detect in google)
Once you made that works on your computer with your webcam, go buy a raspberry pi and a webcam.
OpenCV does work with python so it should be straight forward to convert your C code into Python.
Finally you have to learn how to communicate between your Raspberry and your quadrotor controller, it use some kind of wierd protocols used in RC remote controller.
On that point I can't help since I have never tried this out yet.
