title: Mp3 player with progressBar, with multiple Activity
body: <p>What are the best approach to create a mp3 player, with progress bar update.  BUT, I have to switch between 2 activity, and the mp3 need to continue play\update progress bar  on one of the 2 activity.</p>
  
  <p>On iOS, i can use "singleton" and Notification(or delegate).  On Android, i've heard about "services", but not sure. :)</p>