Child-in-Car tragedy prevention

I can't stop thinking about the tragedy of the little boy left in the car. I'm trying to think of some solution. I know there are some high tech solutions out there but how many parents are going to take the trouble to install them and what about the people that can't afford them?

According to this article, these tragedies happen because parents go into autopilot and there isn't any trigger than helps them remember that there is a baby in back. This danger is especially heightened when there is a change in routine. The parents who think "I would never forget my child in the car" are likely to be the ones who do forget because of that certainty.

Here is my idea for a simple, cheap prevention method:

1. Put a hat on the child seat. This can be a baseball cap or any other kind of hat that you would never normally wear. This should be a special hat that lives in the car, on the child seat. Never wear it for any other occassion.
2. Whenever you put your baby in the seat, put on the hat.
3. When you take the baby out of the seat, put the hat back on the seat.
4. If you are a regular hat wearer and the feeling of a baseball cap just wouldn't register with you, use something else. It should be really outlandish, like maybe one of these plastic rings they have during Halloween with a spider on it, something that you normally wouldn't wear outside of the house.

There you have it, a cheap reminder that there's a baby in the back of your car.