Phone Watermark will let you add your custom watermark to your phone that will be visible across all the phones no matter what application you are using it will always be visible for you unless you stop it.

This application will also work with screen recorders and if you screen record your phone and edit it just to add your watermark to it now you can do it directly while recording your screen.

Note: The app is still in beta and looking for suggestions to improve it further make sure to drop your suggestions!