"Hidden"
Hi,
I remember such a project from upwork. It also captured hidden screenshots from the app. I have already tried it in any many ways and the only way it would work is on a rooted device. Because android OS won't let you reference rootView() of the screen, for security reasons of course. The only other way possible is using google's library called Android-Screenshot-Library(ASL) which is very difficult to use and is very poorly documented.
Deactivating and reactivating the app from dialer codes is not a problem at all, I can easily use android background services for that. I already have a lot of experience with this project so I'll be looking forward to work with you.
Regards.