The National Highway Traffic Safety Administration says more than half of the total deaths in hot cars are children under 2 years old.
But modern technology is rapidly being developed to help prevent those deaths.
The NHTSA estimated nearly 40 children die each year in hot cars, or about one every nine days.
Benjamin Seitz died July 7. His father forgot to drop him at a Connecticut daycare and drove to work, leaving the 15-month-old in the back seat. Benjamin's mother said it can happen to anyone.
"You wake up and have a normal day and then in the afternoon you find out that your son's gone," Lindsey Seitz said.
Safety advocates say it only takes 10 minutes for the temperature inside a car to jump 20 degrees. In one to two hours, the temperature can shoot up 50 degrees.
"Children's bodies heat up three to five times faster than adults' bodies," said Helen Arbogast, of Children's Hospital in Los Angeles.
The NHTSA said there have been 716 child deaths in hot cars since 1998. More than half happened because a child was forgotten.
The Precious Cargo app will send parents a text reminder. A parent types a note like "kids in backseat," sets a time, and the app pushes out the alarm.
The app can also pair with a Bluetooth device to send out an alert when the car stops.
"At 104 degrees, children's bodies begin to shut down," Arbogast said. "At 107 degrees, they can die of heat stroke."
But some people question why automobile companies pour technology into other standard features in automobiles and trucks, but not something to help growing problem children left in cars.
"They're reminding us of everything else," said Janette Fennel, president of KidsandCars.org.
"Quite frankly, you can't buy a car today unless it has a feature that turns your headlights off for you, so who has decided it's more important not to have a dead car battery than a dead baby?"
Another recommendation for parents to remind them they are carrying a child is to put a briefcase or purse behind the driver's seat forcing them to look in the back of their vehicle.
Safety advocates also said that every time parents drive with children, they should "look before they lock."
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