For detecting when an iOS device is shaken when the responder chain isn’t working for you. Handy for debugging. Subclass UIApplication, and pass in the new class name in UIApplicationMain().

ShakeApplication.m

NSString * const ShakeEventNotification = @"ShakeEventNotification";

@implementation ShakeApplication
{
	BOOL _shakeStarted;
}

- (void)sendEvent:(UIEvent *)event
{
    [super sendEvent: event];
    
	if ([event subtype] == UIEventSubtypeMotionShake) {
		// Shake events come in pairs. Only respond to the first.
		if (_shakeStarted) {
			_shakeStarted = NO;
		} else {
			_shakeStarted = YES;
			[[NSNotificationCenter defaultCenter] postNotificationName:ShakeEventNotification object:self];
		}
	}
}

@end