title: Background Access to Microphone in Android
body: <p>Is it possible to be constantly monitoring the microphone from a background application (service?) on an Android phone?</p>
  
  <p>Some idea of what I want to do:</p>
  
  <ul>
  <li>Listen constantly for an audible signal in the background.</li>
  <li>Upon receipt of 'interesting' audio signal, perform some network operation.</li>
  </ul>
  
  <p>The background application must be able to intelligently relinquish access to the microphone should a foreground application require it (unless it can be shared?) - e.g. to make a call.</p>
  
  <p>Is this possible?</p>