The double clicking is silly though, especially since this is a touch device. It's like Apple doesn't even bother coming up with gestures anymore. Why can't we just pinch-to-the-middle the entire screen to bring it up?
I actually think that's a good idea, at least on iPhone. To differentiate it from in-app pinch you could say it has to be from off-screen, like sliding down the notification bar, but from two opposite edges at once.
Wouldn't work on iPad very well, but iPad has the four finger gesture.