A few weeks ago I came across a blog entry by SiliconRepublic (Roy). His original post can be found here:http://siliconrepublic.blogspot.com/2011/02/arduino-based-pc-ambient-lighting.html
The author wrote a small Processing sketch that sums-up all RGB values of his computer display, calculates the mean values and sends them via serial connection to a micro controller (in his case an Arduino). The Arduino controls a strip of RGB LEDs.
That is an easy assembly and really useful at the same time. It appreciates your way of watching movies a lot. My aim was to enhance his ideas so I could have something like the Philips Ambilight: Different colors on different positions of the screen. I also wanted a little user interface so I could easily change parameters without changing my source code.
Because I am not familiar with Processing I used pure Java in this project. I guess you can easily transfer my program to Processing due to the fact that Processing and Java are really similar.
Beside that Java application the other main component you need to accomplish this task is a micro controller (perhaps two?) to operate the LED strips.