title: Can I keep the speech recognizer listening indefinitely?
body: <p>When I call the <code>startListening</code> method of a <code>SpeechRecognizer</code> object, the speech recognizer starts listening for speech. I would like to create a service that is waiting for speech of a specific keyword: when the user says this keyword and the speech recognizer detects this keyword, then the service becomes ready to receive user voice commands.</p>
  
  <p>To this end, after a new <code>SpeechRecognizer</code> instantiated, I should call its <code>startListening</code> method: can I keep the speech recognizer listening indefinitely?</p>