Radio on until door opens

I found this page with some sort of electrical diagram. It's a tutorial on how to make the accessories in your truck stay on until you open the door, like most luxury vehicles do these days. It looks simple enough even though I have a small amount of electrical experience. But I figured you guys would like to see this and we could probably figure this out.

"If you wish to keep the radio (or any other device that is powered by an accessory circuit) on until a door is opened, you can do so by creating a latch when the accessory is turned on with the relay shown below on the left, then breaking ground to the latch when a door is opened as shown with the relay below on the right. While this will keep the radio on, the entire accessory circuit will see 12V+ until a door is opened with the key in the off position."

http://www.the12volt.com/relays/page5.asp#drto