Okay, I'm working on a fun project that has a hurdle where I need to enable Bluetooth audio support for my iOS app.
The hurdle I'm at is that I simply can't even begin to get a list of connected Bluetooth audio devices. Even though my iPhone 5S recognizes my earpiece (a ~3 - 4 year old LG HBM-230, to be precise) and plays audio through it for phone calls, BOTH External Accessory and CoreBluetooth are giving me nothing useful when I query both.
I'm basing my own code off questions & answers I found for both the CoreBluetooth and External Accessory frameworks.
When my code simply tries to "scanForPeripheralsWithServices:nil" for any Bluetooth devices which Settings->Bluetooth say are visible and connected, the below code simply is NOT coming up with a single hit beyond the "CBCentralManagerStatePoweredOn" message in the console.  
And this line in my code (with a valid EAAccessoryManager instance)
NSArray * connectedDevices = [self.eAAccessoryManager connectedAccessories];
also comes back with a nil array.
What could I be doing wrong?
B.T.W., I've made this code available as a GitHub project.
@implementation BluetoothManager
+ (BluetoothManager *)sharedInstance
{
    static dispatch_once_t pred = 0;
    __strong static id _bluetoothMGR = nil;
    dispatch_once(&pred, ^{
        _bluetoothMGR = [[BluetoothManager alloc] init];
    });
    return _bluetoothMGR;
}
- (id)init
{
    self = [super init];
    if(self)
    {
        dispatch_queue_t centralQueue = dispatch_queue_create("com.yo.mycentral", DISPATCH_QUEUE_SERIAL);
        // whether we try this on a queue of "nil" (the main queue) or this separate thread, still not getting results
        self.cbManager = [[CBCentralManager alloc] initWithDelegate:self queue:centralQueue options:nil];
    }
    return self;
}
// this would hit.... if I instantiated this in a storyboard of XIB file
- (void)awakeFromNib
{
    if(!self.cbManager)
        self.cbManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil options:nil];
}
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI {
    NSLog(@"hey I found %@",[advertisementData description]);
}
- (void)centralManager:(CBCentralManager *)central didRetrieveConnectedPeripherals:(NSArray *)peripherals
{
    NSLog( @"I retrieved CONNECTED peripherals");
}
-(void)centralManager:(CBCentralManager *)central didRetrievePeripherals:(NSArray *)peripherals{
    NSLog(@"This is it!");
}
- (void)centralManagerDidUpdateState:(CBCentralManager *)central{
    NSString *messtoshow;
    switch (central.state) {
        case CBCentralManagerStateUnknown:
        {
            messtoshow=@"State unknown, update imminent.";
            break;
        }
        case CBCentralManagerStateResetting:
        {
            messtoshow=@"The connection with the system service was momentarily lost, update imminent.";
            break;
        }
        case CBCentralManagerStateUnsupported:
        {
            messtoshow=@"The platform doesn't support Bluetooth Low Energy";
            break;
        }
        case CBCentralManagerStateUnauthorized:
        {
            messtoshow=@"The app is not authorized to use Bluetooth Low Energy";
            break;
        }
        case CBCentralManagerStatePoweredOff:
        {
            messtoshow=@"Bluetooth is currently powered off.";
            break;
        }
        case CBCentralManagerStatePoweredOn:
        {
            messtoshow=@"Bluetooth is currently powered on and available to use.";
            NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], CBCentralManagerScanOptionAllowDuplicatesKey, nil];
            [_cbManager scanForPeripheralsWithServices:nil options:options];
            break;
        }   
    }
    NSLog(@"%@", messtoshow);
}
@end