There's a burglary tool out for some vehicles (BMW?) that bypasses immobilizers when plugged into the OBD-II port, so those who are paranoid will drop the coin for a port lock. In addition, I know that some non-VAG factory scan tools will perform unsolicited re-flashes of every controller in a vehicle when plugged in at the dealer, so those with, um, custom firmware or cases where the firmware updates add unwanted features/annoyances sometimes buy this (or the cheaper non-locking "do not flash" plastic OBD-II port cover). As an example of the feature thing, Dodge added a safety feature retrofit where the horns in their HD pickups will beep if the driver's side door is open with the truck in reverse. While this may sound like a good idea since they were having issues with automatic owners putting their truck into reverse instead of park and getting out, there are apparently a lot of people who regularly tow trailers with these HD trucks and somehow approach them in reverse with the door open to align the ball when hitching up. A blaring horn in your driveway at 5:00 AM when hitching up your camper for a trip is a sure way to piss your neighbors off.I couldn't believe that there was a need for a lock on the car's OBDII connector. But maybe things are radically different down here in the antipodes! Is there a serious application for these devices up in the US?