No More uses the Safari Content Blocker API. It lets us tell the browser on your iPhone what it's allowed to show. It's also private – there's no way for us to tell what you do when you're using the apps.
One unfortunate limitation of the Content Blocker API and of how native iPhone apps work is that I can only build No More to work on web apps. The web was built on open, accessible technologies that make things like content blocking possible. Native iPhone apps, like the ones you get in the App Store, are quite closed. They run in a very secure, very locked-down sandbox; where the web allows me to see the code running in Safari and therefore to craft rules that interact with it, there's nothing that Apple offers for me to do the same thing.