Have 2 finger drag call a method, but not interact with a UIScrollView

Question

I have a view with a UIScrollView that contains a UIImageView. The UIScrollview does not occupy 100% of the screen, like so:

View
---> UIScrollView (size is approx 200 x 200 px)
`----> UIImageView

I want to enable 2 finger drag 'anywhere' on the screen, which will call a method, but this drag will have no effect of the functionality of the UIScrollView, which can pinch, zoom, drag, etc.

I was thinking of doing this by overlaying a 'dummy' UIView that is 320 x 480 px, like so:

View
---> UIView ('transparent'/dummy view, sized to 100% of screen)
---> UIScrollView
`----> UIImageView

and having it capture all the 2 finger drag(s), but is there a simpler (more elegant) way to do this? Could I simply overlay a 200 x 200 px UIView over my UIScrollView (which is the same size)?