title: How do I start a long-living background task?
body: <p>i write a Demo App in WP7, the App has 2 Counter, the second counter should work 
  in background even if the App is Closed. 
  Like background work in iOS:
  <code>beginBackgroundTaskWithExpirationHandler</code> 
  or Services in Android.</p>
  
  <p>thanks</p>