Craft as a CMS for mobile app content
This is most likely possible by serving up restful resources that refer to Craft data with some sort of PHP API that you'll need to write. The APIs you write will just need to grab data using Craft's API

As for hiding certain content for mobile (or whatever frontend platform), I'd create a Lightswitch field for section that you can use to signify content that is "mobile only" or whatever you'd like.

BTW - your API doesn't even necessarily need to be in PHP - You can probably use AngularJS or some other JS server-side framework and use Twig templating. Someone correct me if I'm wrong about that... The great thing about Craft CMS is it's frontend-agnostic