CallKit - Call Detection

Hi,

I need to monitor in my app which interacts with BLE when a user is on the phone or not due to a limitation with some devices and BLE. I've written a basic call observer to test - but when the application is backgrounded it is not receiving any updates. I was wondering if anyone knew how to get call status notifications in the background?

class ViewController: UIViewController{
  @IBOutlet weak var callStatusLabel: UILabel!
  var callObs : CXCallObserver!

  override func viewDidLoad() {
    super.viewDidLoad()
    /
    callObs = CXCallObserver()
    callObs.setDelegate(self, queue: nil)
    print("Monitoring Calls")
    callStatusLabel.text = "Monitoring..."
    self.view.backgroundColor = UIColor.yellow
  }
  override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    /
  }

}
extension ViewController : CXCallObserverDelegate
{
  func callObserver(_: CXCallObserver, callChanged: CXCall)
  {
    if(callChanged.hasEnded)
    {
      print("Call Ended")
      callStatusLabel.text = "Call Ended"
      self.view.backgroundColor = UIColor.green
    }
    else if(callChanged.hasConnected)
    {
      print("Call Connected")
      callStatusLabel.text = "Call Connected"
      self.view.backgroundColor = UIColor.red
    }
  }
}

I currently have the following Background modes enabled:

• Audio, AirPlay & PIP
• Loc Updates
• VOIP
• External accessory comm
• Uses BLE
• Background Fetch