var granted = await CrossSpeechRecognition.Current.RequestPermission();
if (granted) 
{
    // go!
}

var listener = CrossSpeechRecognition
    .Current
    .ContinuousDictation()
    .Subscribe(phrase => {
        // will keep returning phrases as pause is observed
    });

// make sure to dispose to stop listening
listener.Dispose();

CrossSpeechRecognition
    .Current
    .ListenUntilPause()
    .Subscribe(phrase => {})

CrossSpeechRecognition
    .Current
    .ListenForKeywords("yes", "no")
    .Subscribe(firstKeywordHeard => {})

CrossSpeechRecognition
    .Current
    .WhenListenStatusChanged()
    .Subscribe(isListening => { you can talk if this is true });