Proponents note that most vehicles alert drivers when they forget their keys in the ignition, leave the headlights on or fail to close a door. They say it should be no different when you forget your kid. "Technologies alerting drivers to check their backseats for children exists today but has not been widely deployed," Congressman Frank Pallone, Jr. (D-NJ) said in a hearing today.

In a statement, the Alliance of Automobile Manufacturers said it will carefully review any legislative proposals. It added that fewer than 13 percent of new car buyers have a child under six years old and it takes about two decades for new technology to reach all passenger vehicles on the road. Increased public awareness is a faster path to safety, the Alliance says.

There's no question that car manufacturers are developing more advanced safety systems. Earlier this week, Chevrolet announced a new feature that prevents teens from shifting out of park until they buckle. And retrofitting vehicles may be easier in the future when more automakers adopt over-the-air software updates. But the legislation could raise the question of which technologies to make mandatory. "If an automotive feature or technology proves it can save lives, it should not be a luxury reserved only for those who can afford to buy the highest end cars," Congressman Pallone said.