This is just totally the wrong way to fix the problem. Enhance penalties for those who leave their children in cars. Also, I can think of a half dozen reasons this wouldn't work. Think about it, if you have bags of groceries in your back seat and the vehicle senses the weight of the bags and next thing you know the alarm is going off. How else would the car sense children in the car? Motion sensors? This would make cars more expensive among other problems.