I have always heard about using temporary tattoos on your kids when you go on field trips to big places like the zoo. However when I looked them up to actually order them with all the information needed I about had a heart attack.
Lately I have been seeing a neato do it your self type that will work and seems to hold up better against water and sweat.
All you need is some Liquid Bandage costs about $5-$6 at Wal-Mart or CVS and has multiple uses in your home for later.
Next you need a simple Sharpie marker, I suggest fine tip so that you can easily write with it. They run about $2 at Wal-Mart.
Then all you have to do is pick a place on the child (arm, wrist, etc) and write your emergency telephone number and name on them. Make sure marker is dry and then coat over the whole area with the liquid bandage a time or two. This will allow it to be in place as well as waterproof. This is good for water parks or excessive sweating.
Hope this can help some of you worry wort mama's like me!