title: telprompt - can I get the call duration?
body: <p>I am trying to make a call through the telpromt command to return to my application after it makes a call:</p>
  
  <pre><code>NSString *telno = @"telprompt://121,,,,14";
  [[UIApplication sharedApplication] openURL:[NSURL URLWithString:telno]];
  </code></pre>
  
  <p>Is there any way to calculate call duration in all situations from my app?</p>