I think at least a few car companies have some sort of warning system already. But with some babies weighing less than 10 pounds, that’s a requires a very precise pressure sensor. A built-in heat sensor might detect hot food and not detect the difference between sun-heated surfaces and an infant. Motion detectors might notice balloons, but not a sleeping infant.
Current suggestions include putting your briefcase, wallet, or purse next to the carseat, something you’ll need when you leave the car. Or placing a stuffed animal in the front seat so you’ll be reminded to look in the back. Every strategy has its flaws.
This was certainly an unintended consequence of installing airbags in cars to protect drivers and passengers…