title: UINavigationItem with prompt and activity indicator
body: <p>I'm wondering how Apple implemented the UINavigationItem that contains an activity indicator (see attached image below), above the title. Is this Apple's private API that allows to do that? If not, how can it be reproduced in an application.</p>
  
  <p><a href="http://img218.imageshack.us/img218/8819/img0133g.png" rel="nofollow noreferrer">UINavigationItem with prompt and activity indicator http://img218.imageshack.us/img218/8819/img0133g.png</a></p>
  
  <p>Thanks!</p>