The ‘Interactive Short-Range Motion Sensing Devices’ which Tesla plans to use, is based on an interactive short-range motion sensing device and aims to help detect when a child has been left behind in a car.
Tesla is applying with the Federal Communications Commission (FCC) for approval for the use of the new sensor, Electrek had said while quoting Reuters reports.

“Tesla’s device would utilize four transmit and three receive antennas driven by a radar front-end unit. Tesla says millimeter-wave radar technology has advantages over other sensing systems like camera-based or in-seat occupant detection systems.”

The automaker announced that the radar-based device “provides depth perception and is able to ‘see’ through soft materials, including a blanket that covers a child in the child restraint.”
According to NHTSA, last year in the US, more than 50 kids died while left behind in hot cars.
But the new system goes even further than detecting children. Tesla writes in the application that “micromovements such as respiration patterns and heart speeds” can be detected
Such features could be useful as a monitoring function for the driver. Tesla also claims that the radar-based system is more effective in measuring body sizes than weight sensors and will also be more reliable in maximizing the deployment of airbags in an accident.
Until granting approval, the FCC is calling for feedback on the application until September 21 – meaning that the system will possibly not go into production cars until next year.