PIP-Camera on iPad

Hi there,
I try to find an app for the iPad, which I can’t find.
I‘d like to have a selfie cam window picture-in-picture (PiP). Like the window of FaceTime while you make a videocall. While you are in another app, I can see the other one pip.
I‘d like to take a screencast with a video of myself in one corner and the rest what ever I want to show.
Do you know such an app?
Thank you!

Developers aren’t allowed to use the camera when the app isn’t open, so an app like this can’t exist with the current limitations of iOS.

It‘s a pity. Thank you for the information.