【Watch Fast Five Online】

It can Watch Fast Five Onlinebe as simple (and stinky) as forgetting leftovers in the back seat, or as tragic and terrifying as leaving a pet or young child sitting in the back while a car heats up in the summer sun. That's where Nissan's "smart" alert system comes in.

Nissan's rear door alert — or RDA — system was first introduced in the Nissan Pathfinder last year. The recently patented technology triggers the horn and a message display through door sensors alerting drivers to check the back seat after the car is parked if the back door was opened before the ride started. The tech was filed as an "activity monitoring apparatus."

On Tuesday, the car maker announced that its 2019 models for eight cars, including the Rogue and Altima, would include the alert system. By 2022 RDA will be included on all four-door trucks, sedans, and SUVs.

The fairly simple technology works by monitoring the rear door — is it opened and closed before and after the car starts? If you opened the back door before a trip but never reopened after the car is off, the system will start with a notification on the dashboard. Eventually the car will begin "chirping" louder and louder through the horn. (You can turn it off through the console, or by opening the door.)

It's not constantly beeping at you — only if you opened the back doors and you need a reminder or three to grab what you left back there.

Here's what the alert sounds like:

The idea came from the super-scary possibility of leaving kids in a baking vehicle, which can get fatally hot very quickly, even in cooler temperatures. Note: Tuesday is National Heatstroke Prevention Day, which is part of a child safety campaign through the National Highway Traffic Safety Administration.

Mechanical engineer Marlene Mendoza helped create the RDA technology when she left a pan of lasagna in the back of her car. She was pregnant at the time, and it spurred the alert idea. "The worst thing was the car smelled for days, but it made me ask myself, 'What if I left something far more important back there?’" she asked in a release from Nissan. She co-created the tech with engineer Elsa Foley.

While it seems exceedingly simple, it's a pretty brilliant back-up system for our busy schedules and easily distracted minds.