How to detect shake gestures in a UIViewController.

ViewController.m

@implementation ViewController

#pragma mark - UIResponder

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event
{
    if (motion == UIEventSubtypeMotionShake) {
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Shaken"
                                                            message:@"Not stirred."
                                                           delegate:self
                                                  cancelButtonTitle:@"OK"
                                                  otherButtonTitles:nil];
        [alertView show];
    }
}

- (BOOL)canBecomeFirstResponder
{
    return YES;
}