No meu projeto, eu usoAVAudioSession para detectar qualquer fone de ouvido está conectado ou desconectado. Mas, neste caso, não consigo detectar quando o dispositivo bluetooth está conectado. Aqui está o meu código para o estado dos fones de ouvido.

 - (void)audioRouteChangeListenerCallback:(NSNotification*)notification
    {

    NSDictionary *interuptionDict = notification.userInfo;

    NSInteger routeChangeReason = [[interuptionDict valueForKey:AVAudioSessionRouteChangeReasonKey] integerValue];

    switch (routeChangeReason) {

        case AVAudioSessionRouteChangeReasonNewDeviceAvailable:
            //NSLog(@"AVAudioSessionRouteChangeReasonNewDeviceAvailable");

            NSLog(@"Headphone/Line plugged in");

            [_soundButtonOutlet setImage:[UIImage imageNamed:@"sound-on.png"] forState:UIControlStateNormal];

            _headSetState=YES;

            break;

        case AVAudioSessionRouteChangeReasonOldDeviceUnavailable:
            NSLog(@"AVAudioSessionRouteChangeReasonOldDeviceUnavailable");

            NSLog(@"Headphone/Line was pulled. Stopping player....");

             [_soundButtonOutlet setImage:[UIImage imageNamed:@"sound-off.png"] forState:UIControlStateNormal];
            if(_isPlaying==YES)
            {


            [self.player pause];

            [_audioButtonOutlet setImage:[UIImage imageNamed:@"play.png"] forState:UIControlStateNormal];

            _isPlaying=NO;

            }
            _headSetState=NO;

            break;

        case AVAudioSessionRouteChangeReasonCategoryChange:
            // called at start - also when other audio wants to play
            NSLog(@"AVAudioSessionRouteChangeReasonCategoryChange");


            break;
    }



- (BOOL)isHeadsetPluggedIn

{

    AVAudioSessionRouteDescription* route = [[AVAudioSession sharedInstance] currentRoute];
    for (AVAudioSessionPortDescription* desc in [route outputs]) {

        if ([[desc portType] isEqualToString:AVAudioSessionPortHeadphones])
        {
        [_soundButtonOutlet setImage:[UIImage imageNamed:@"sound-on.png"] forState:UIControlStateNormal];
            _headSetState=YES;
            return YES;
        }
        else
        {
    [_soundButtonOutlet setImage:[UIImage imageNamed:@"sound-off.png"] forState:UIControlStateNormal];
            _headSetState=NO;
            return NO;

        }
    }


    return NO;
}

}


- viewWillAppear  {

 [AVAudioSession sharedInstance];

  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(audioRouteChangeListenerCallback:) name:AVAudioSessionRouteChangeNotification object:nil];

[self isHeadsetPluggedIn];

}

Então, como posso detectar se um fone de ouvido bluetooth está conectado ou não ao iOS 8?