title: How do I detect a touch over a specific area
body: <p>Currently I see that a touch event will show me the UIView where the touch occured. But what if I need to detect a touch of some non rectangular shape, like a circle.  How would I go about doing something like that ?</p>
  
  <p>Basically I want to do something only if the user touches somewhere within a circular area that's not visible.</p>
  
  <p>Any help/direction is appreciated, TIA!</p>