title: Google API: Notify about Calendar Entry Change via Google Talk
body: <p>I have a calendar and some Users in Google Talk, which I'd like to notify when the event has changed.</p>
  
  <p>So I will need to use the Calendar API and the Talk API, both are enabled in the API Console.</p>
  
  <p>Does anyone have an idea how I could make use of this? Preferably using PHP.</p>
  
  <p>Maybe this has been done before or is usable by other people. Thanks in advance for the answers!</p>