public sealed class DeviceLocationSourceChangedEvent : ArcGIS.Core.Events.CompositePresentationEvent<DeviceLocationSourceChangedEventArgs> 

private void SubscribeToSourceEvents()
{
  DeviceLocationSourceChangedEvent.Subscribe(OnDeviceLocationSourceChanged);
}
private void OnDeviceLocationSourceChanged(DeviceLocationSourceChangedEventArgs args)
{
  if (args == null)
    return;

  var source = args.DeviceLocationSource; 

  //  TODO - something with the updated source properties
}