An over-the-air update has added new functionality to the Model S, X and 3, but it only comes into force when the car is parked. Dog owners, get excited.

Tesla has added two new software features to the Model S, X and 3, thanks to one of its over-the-air updates.

The first is Sentry Mode, designed to deter potential thieves. If someone leans on a car with Sentry activated, the car switches into an 'Alert' state and shows a message on the central touchscreen, warning the potential thief the car's cameras are turned on.

If something more severe (like a broken window) is detected, the car activates its alarm, cranks up the brightness on the centre display, and plays music at full volume through the car stereo. A picture of the 'Alert' stage is below, from Reddit user u/Spamium.

Owners will also be notified on their Tesla application if the system has been activated, too. The feature isn't automatically turned on, though. It needs to be activated once the car is parked, and a formatted USB needs to be plugged in to record video footage.

The second feature in the over-the-air update is Dog Mode. Like children, it's dangerous to leave pets locked in your car on hot days, with in-cabin temperatures often doubling once the vehicle is unattended.

With Dog Mode activated, the car will keep the air-conditioning at a preset temperature, and display a message on the central touchscreen to alert passersby.

Given some vigilantes have taken to breaking windows when they see dogs locked in cars on hot days, the message is probably a good idea.