// Drop a custom view into XIB and set its class to MASShortcutView
@property (nonatomic, weak) IBOutlet MASShortcutView *shortcutView;
	
// Think up a preference key to store a global shortcut between launches
NSString *const kPreferenceGlobalShortcut = @"GlobalShortcut";

// Assign the preference key and the shortcut view will take care of persistence
self.shortcutView.associatedUserDefaultsKey = kPreferenceGlobalShortcut;

// Execute your block of code automatically when user triggers a shortcut from preferences
[MASShortcut registerGlobalShortcutWithUserDefaultsKey:kPreferenceGlobalShortcut handler:^{
    // Let me know if you find a better or more convenient API.
}];

// Declare an ivar for key path in the user defaults controller
NSString *_observableKeyPath;
    
// Make a global context reference
void *kGlobalShortcutContext = &kGlobalShortcutContext;
    
// Implement when loading view
_observableKeyPath = [@"values." stringByAppendingString:kPreferenceGlobalShortcut];
[[NSUserDefaultsController sharedUserDefaultsController] addObserver:self forKeyPath:_observableKeyPath
                                                             options:NSKeyValueObservingOptionInitial
                                                             context:kGlobalShortcutContext];

// Capture the KVO change and do something
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)obj
                        change:(NSDictionary *)change context:(void *)ctx
{
    if (ctx == kGlobalShortcutContext) {
        NSLog(@"Shortcut has changed");
    }
    else {
        [super observeValueForKeyPath:keyPath ofObject:obj change:change context:ctx];
    }
}

// Do not forget to remove the observer
[[NSUserDefaultsController sharedUserDefaultsController] removeObserver:self
                                                             forKeyPath:_observableKeyPath
                                                                context:kGlobalShortcutContext];