How to capture Tap gesture on MKMapView

You can use a UIGestureRecognizer to detect touches on the map view.

Instead of a single tap, however, I would suggest looking for a double tap (UITapGestureRecognizer) or a long press (UILongPressGestureRecognizer). A single tap might interfere with the user trying to single tap on the pin or callout itself.

In the place where you setup the map view (in viewDidLoad for example), attach the gesture recognizer to the map view:

UITapGestureRecognizer *tgr = [[UITapGestureRecognizer alloc] 
    initWithTarget:self action:@selector(handleGesture:)];
tgr.numberOfTapsRequired = 2;
tgr.numberOfTouchesRequired = 1;
[mapView addGestureRecognizer:tgr];
[tgr release];

or to use a long press:

UILongPressGestureRecognizer *lpgr = [[UILongPressGestureRecognizer alloc] 
    initWithTarget:self action:@selector(handleGesture:)];
lpgr.minimumPressDuration = 2.0;  //user must press for 2 seconds
[mapView addGestureRecognizer:lpgr];
[lpgr release];

In the handleGesture: method:

- (void)handleGesture:(UIGestureRecognizer *)gestureRecognizer
{
    if (gestureRecognizer.state != UIGestureRecognizerStateEnded)
        return;

    CGPoint touchPoint = [gestureRecognizer locationInView:mapView];
    CLLocationCoordinate2D touchMapCoordinate = 
        [mapView convertPoint:touchPoint toCoordinateFromView:mapView];

    MKPointAnnotation *pa = [[MKPointAnnotation alloc] init];
    pa.coordinate = touchMapCoordinate;
    pa.title = @"Hello";
    [mapView addAnnotation:pa];
    [pa release];
}