App that display's note on screen if lost?

Hello,
I have recently added a PIN to my phone, but on previous phones (many moons ago), I was able to add amessage to the screen, telling the finder who to call - and it worked, I got my phone back safe and sound (Nice to think there are some nice honest people in the world!!!)

But with the PIN lock, this isn't an option, so i have no chance of getting the phone back.

Is there an App that would help me put a message on the screen eevrytime it is locked?

Thanks!