How the heck can you forget your child/grandchild in a car? I mean, you remember to turn off the ignition, take the keys, close the door (and lock it), YET forget that a baby is in the car?!
I've seen it happen (not resulting in death, though), read about it happening...maybe each case should be considered on its own merit.
It seems the complaint here is lack of personal responisiblity, but you want to enable more lack of responsibility by creating features to remind caretakers (parents, etc) that a child is inside so they can pay less attention?
I don't get it.