SpringBoard prototype settings:
I didn't think people would find it too interesting when I posted it so I didn't bother to document it. But anyway, here's how it works.

There's a class in SpringBoard called SBPrototypeController. Apple use it internally so they can easily tweak values for animations etc. without having to make a change in the source, recompile and reinstall. SBPrototypeController has a class method called reloadDefaults that determines whether to allow this. Here's what is does:

+ (void)reloadDefaults {
    if ([[SBPlatformController sharedInstance]isInternalInstall])
        if (NSClassFromString(@"PTSettingsController"))
            if ([[NSUserDefaults standardUserDefaults]boolForKey:@"SBPrototypeSettingsEnabled"])
                [_sharedInstance _configureForDefaults];

So it starts by checking with SBPlatformController as to whether you're running an internal install. SBPlatformController gets this info by asking libmobilegestalt: MGCopyBoolAnswer(CFSTR("apple-internal-install"));
Libmobilegestalt checks for the existence of /AppleInternal/Library/PreferenceBundles/Internal Settings.bundle using the c function "stat". If that bundle exists, it returns that you're running an internal install so you pass the first step.

The next step is a runtime check for the existence of the class PTSettingsController. This class is part of a private framework called PrototypeTools, which apple removed before seeding beta 1. So on stock firmware this check fails. However this framework is available via the SDK so it can be copied over to /System/Library/PrivateFrameworks

The final step is the check for SBPrototypeSettingsEnabled in NSUserDefaults. Since the code is run in SpringBoard, the code simply checks the com.apple.springboard.plist preference file for that key.

After passing all those steps, SBPrototypeController registers itself as a "volume bandit" in the _configureForDefaults method. It steals volume events. So when volume up is pressed, it slides up. When volume down is pressed (or the done button is pressed), it goes away.