See Model X Enhanced Anti-Theft The interior dome light assembly is replaced with one that incorporates two motion sensors, and then presumably a firmware upgrade is needed to tie them into the onboard computer so it can activate the horn in some manner if motion in the cabin is detected, or the vehicle moves a certain amount, after the car locks itself and the fob is a sufficient distance away that it is no longer detected. Here is an article about an X owner having it installed First look at Tesla’s new Enhanced Anti-Theft system The owner is quoted as saying: “Here in the SF Bay Area, Teslas unfortunately have been quite a magnet for petty “smash and grab” incidents. Teslas in Northern California being as plentiful as they are seem to attract car thieves for some particular reason. So any chance to add extra security to the vehicle seems like a no-brainer.” ————————————————————————————————————— I am doubtful that such a system would be much of a deterrent to those who smash car side windows just to grab whatever might be lying on the seats or on the floor. Yes, the Enhanced Anti-Theft system comes with two small stickers to place on the side windows which presumably state that the vehicle is protected by an alarm, but that is unlikely to deter many thieves, in my opinion. I had my X driver side rear window smashed last year when the car was parked under a street light near the California Academy of Sciences in Golden Gate Park while I was attending an evening lecture there. Nothing was taken from the car because there was almost nothing to take. The new Tesla Enhanced Anti-Theft system does not appear to detect the sound of a breaking window, but presumably the movement of window glass pieces into the cabin would trigger the motion sensor. Still, the sound of a car alarm is something that city and suburban dwellers are so accustomed to that I don’t regard it as much of a deterrent. I have little concern about my car being stolen, but am concerned about smash-and-grab attacks.