That technology was pioneered by two Nissan engineers, Elsa Foley and Marlene Mendoza. They'd been working on the project for a while when something happened that brought home the gravity of what they were doing, and it involved a tray of pasta:
"We...knew we were on the right track one morning when Marlene discovered she had left a pan of lasagna in the back seat of her car one night after coming home after a long day at the office," said Foley. "The worst thing was the car smelled for days, but it made me ask myself, 'what if that had been something else back there?'"
The technology has now been finalized, and it's called Rear Door Alert. It senses when a car's rear door has been opened before a trip begins--for example, when a driver has put a child or pet in the back seat. If the trip ends and the vehicle is turned off without the rear door being opened again, Rear Door Alert can issue notices on the dashboard and sound a series of alarms using the vehicle's horn.
Obviously, there are plenty of instances in which owners might put something in the rear seat and mean to leave it there over multiple stops--luggage, groceries, and so on. Rear Door Alert can be turned off altogether for folks who don't have to worry about leaving kids or pets in the back seat, or it can be temporarily silenced via the instrument cluster.
Rear Door Alert is part of Nissan's "Intelligent Mobility" initiative, which aims to achieve a fleet that has zero emissions and is involved in zero accidents. Rear Door Alert will be standard equipment on the 2018 Nissan Pathfinder when it rolls out this September. Other models will follow.