People like personalizing their possessions and the more expensive something is the more personalized the owner would probably prefer it to be. A car is likely the second most expensive thing someone owns, after their house. Most modern cars beep an acknowledgement when the associated keychain radio transmitter is clicked. It just beeps? Didn’t cell phones stop “just beeping” like 5 years ago, while nice phones had basic ringtones at least 10 years ago?
So, here is the idea. What if you could use a USB connection in your dashboard to load a 1-5 second audio clip that plays (midi-fied?) instead of beeping when the radio transmitter is used? You could even permit a set of them to be loaded, so that “lock”, “unlock”, and “find me” can have different audio settings.