Watch source change (Headphone vs. Internal Speaker)

watchSound.m

NSLog(@"Starting");
  AudioDeviceID defaultDevice = 0;
  UInt32 defaultSize = sizeof(AudioDeviceID);
  
  const AudioObjectPropertyAddress defaultAddr = {
    kAudioHardwarePropertyDefaultOutputDevice,
    kAudioObjectPropertyScopeGlobal,
    kAudioObjectPropertyElementMaster
  };
  
  AudioObjectGetPropertyData(kAudioObjectSystemObject, &defaultAddr, 0, NULL, &defaultSize, &defaultDevice);

  AudioObjectPropertyAddress sourceAddr;
  sourceAddr.mSelector = kAudioDevicePropertyDataSource;
  sourceAddr.mScope = kAudioDevicePropertyScopeOutput;
  sourceAddr.mElement = kAudioObjectPropertyElementMaster;

  
  AudioObjectAddPropertyListenerBlock(defaultDevice, &sourceAddr, dispatch_get_current_queue(), ^(UInt32 inNumberAddresses, const AudioObjectPropertyAddress *inAddresses) {

    
    UInt32 dataSourceId = 0;
    UInt32 dataSourceIdSize = sizeof(UInt32);
    AudioObjectGetPropertyData(defaultDevice, &sourceAddr, 0, NULL, &dataSourceIdSize, &dataSourceId);
    NSLog(@"Input changed");
    if (dataSourceId == 'ispk') {
      NSLog(@"Internal Speaker");
    } else if (dataSourceId == 'hdpn') {
      NSLog(@"Headphone");
    }
  });