At work each month, we have a staff meeting. Over the past few months, we have started each of these meeting with a "safety moment" highlighting some particular topic of safety.
The one presented today was a great idea and I thought I'd pass it on to you.....we were talking about children getting lost at the zoo, mall, etc. A mom has come up with temporary tattoos that are personalized with your cell phone number that you can rub on your child's arm before you head out. That way, if you are separated somehow, there is an instant way for contact with you. The website is www.safetytat.com. It also has several different options for identifying food allergies, autistic/non verbal children, etc which could prove very helpful in situations where your child is not well known.
Another idea mentioned was to take a photo of your child as you are entering the amusement park or whatever (on your digital camera or phone - which you all carry all the time, right?!) so that you have exactly what the child looks like that day and what they are wearing (because really, do you remember what clothes you put on your child each day?)
One last item of note was to somehow mark or label your stroller -- so many look alike and it could keep you or someone else from just walking off without looking closely that it is your child in the stroller! We label our suitcases when we travel, but many strollers probably don't have any sort of identifying marks on them or contact info for you.
All these things would be meaningless if someone was maliciously trying to take your child, but could prove very helpful if you are accidentally separated!