I know that the iphone has a security feature where all your data can be set to be wiped if the user incorrectly attempts to log into the phone several times.
What about a third party app that makes your phone be annoying in the event it was stolen and someone was incorrectly attempting to access your phone.
Maybe on the third attempt it could say “sorry try again”. Then on the fourth attempt a fake home screen jpeg could be displayed, then when they try and select and app, it says, “Just messing with you. You don’t belong inside this phone. Give it back. Really, don’t be an ass, give me my phone back.
Some other ideas after a certain number of incorrect attempts have been tried:
-The credits from Monty Python and the Holy Grail play on repeat with all the flashing and the llama’s
-Random incredibly unexciting histroy facts are recited in a monotone voice
-A recording of Richard Simons repeatedly encourages the theif that they can do it, then the battery dies