You assume in that a world full of beeping back up alarms a child or pet (or anybody, for that matter) would recognize that one more means move.

My guess they would ignore the sound the same way they ignore the sound of a nearby car starting already. And I'm not sure I want every car in the parking lot beeping all the freakin' time.

When I lived in a college dorm, every morning the cafeteria truck would back-up to the dock at five am and wake me.

When I rented a vehicle that had one (and a door open alarm with the same sound) every time we parked or left the parking lot, we'd be beeping away with people staring at us.

I curse those darn things.

But like Hyenuf said, the people actually standing in the way are likely to be oblivious--on a cell phone or fussing with a receipt or something--otherwise they'd see you get in your car; or the child won't know what the noise means.

Remember in the 80's when the DOT made US cars have a 'beep-beep' (high note) horn instead of a 'honk-honk', because it was more likely to make people look? Eventually they discovered people were looking because they wanted to see the little sports-car that made that sound--when the same sound came from a boring sedan, they stopped looking. Changed that law. I think the same for this. If every car beeped, no one would notice.

To clarify...in my car, the back up sound is heard only inside the car- The sounds gets faster as you approach an object, letting you know the distance between your car and the object. The sound is to warn the driver, not the outside world. I would agree that a cacaphony of beeps in a parking lot would be confusing and not helpful. Sorry for the inaccurate description.

Go to Radio Shack, buy cheap wireless motion-sensor alarm, install sensors on rear bumper (use a good quality adhesive). Mount on/off switch prominently on the dash.

Or, walk around the vehicle before getting in and starting it up, also checking to see if lights are functioning and tires are properly inflated, etc., as I've done every time I drive for the past 40 years (former professional driver, old habits die hard).