"YOU want people to buy a device that solves a problem that is almost non-existant. I'm not aware of any child that has died, or even been injured as a result of being left behind in a bus."
That is very callous of you to write that because leaving a child on a bus happens more frequently than you think and you can't deny that there is some psychological trauma suffered when a child is left alone in a strange place, such as an abandoned school bus,,,,,,, not to mention the frightening experience for the parents.
And, yes, I do agree with some of your comments, just not that one!