Since we can assume that there are no public APIs that support tethering setup, we can also assume that it's still possible for them to be used in rogue apps and for developers to have access to private data.
Apple rejects apps that use private APIs.
Couldn't you write the instructions necessary to make the private API call on the stack at runtime and then simply execute an assembly jump instruction?
Even better/worse, you also have direct access to the camera(s), which means you don't need to prompt the user or display anything on-screen to capture photos or video.
I know Android clearly warns users about an app's capabilities. Does anyone know if that opt-in, or is it derived by some type of code analysis?
However, during app runtime, only those listed capabalities are provided to app. If the app tried to use something else, it would get exception. Short of bug in the platform, there is no way getting around.