title: How to collapse Android notifications?
body: <p>I'm sending a C2DM update to my Android app every 1/2 hour, which creates a Notification. Problem is, when I wake up in the morning I get 15 Notifications queued up in the status bar. </p>
  
  <p>How do I only keep the latest notification, overwriting previous ones?</p>
  
  <p>I tried looking at the C2DM documentation (<a href="http://code.google.com/android/c2dm/" rel="nofollow noreferrer">http://code.google.com/android/c2dm/</a>) which mentions a parameter called collapse_key, but I couldn't find an explanation for how to use it, nor am I sure the solution lies on the C2DM side.</p>
  
  <p>Thanks!</p>