I'm also struggling with calling the extension, but in my case I don't think its working at all. When you say you can shield apps with a toggle, are you doing that in your main app? I was under the impression that shielding had to be done in the extension by calling center.startMonitoring(), but if it can be done without it I think that would be fine for my purposes. If you have any insight on this, it would be greatly appreciated!