Hey, cool thread! I like secret passageways. I've always thought that the classic "pull the book out in the bookcase and it opens the door" thing was really neat!
If the house is being designed right now (or will be in the future) you're set. It's just a matter of building in a fake wall, to hide the crawl space/passageway in back of it.
What RU trying to do,make a "back way out?" RU one of those Militia Men and you're afraid of The Man coming to get you? Technology has rendered nobody invisible. Infrared scanners that see thru walls (and secret passageways) have been around for years.
But, if this is to get away from burglars/inlaws, then I understand completely! Start searching the internet, buddy and good luck to you.!