IPhone : Flashing LED iPhone

I am making an app that has a flashlight as part of it. I have this in my ViewDidLoad

    AVCaptureSession * session = [[AVCaptureSession alloc] init];

[session beginConfiguration];

AVCaptureDevice * device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

if ([device hasTorch] && [device hasFlash]){
    [device lockForConfiguration:nil];
    [device setTorchMode:AVCaptureTorchModeOn];
    [device setFlashMode:AVCaptureFlashModeOn];
    [device unlockForConfiguration];


    AVCaptureDeviceInput * flashInput = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
    if (flashInput && ([audioPlayer isPlaying] == true)){
        [session addInput:flashInput];

    }
    AVCaptureVideoDataOutput * output = [[AVCaptureVideoDataOutput alloc] init];
    [session addOutput:output];
    [output release];
    [session commitConfiguration];
    [session startRunning];

}

[session release];

That makes the flashlight go on without a problem.

I want the LED to flash rapidly, maybe even sending out an SOS in morse code if possible.

Is that possible, and if so what should I add to my code?