How to put an overlay on an android without recording ?

I would like to screen my phone (phone 1) with an other phone (phone 2 ), and I would like to set up an overlay on the phone 1, do you know any program I could use ?

It's just to set up a fake gold number.

I found how to do it on post prod, but it would mean I would have to launch a video on phone 1 and record with the phone 2, wich is boring if I want to scale what I'm on.

Thanks for reply