The United State's Federal Bureau of Investigation (FBI) has it's very own (first) iPhone APP -- called 'FBI Child ID' it is designed to allow parents to have a place to store information on their child/ren including photos, physical identifiers, nicknames, etc. This free App is compatible with iPhone, iPod touch, and iPad - but does require iOS 4.2 or later
Here is the official description taken from the Apps iTunes page:
The free FBI Child ID app provides a convenient place to electronically store photos and vital information about your child so that it’s literally right at hand if your child goes missing. You can show the pictures and provide physical identifiers such as height and weight to security or police officers on the spot. Using a special tab on the app, you can also quickly and easily e-mail the information to authorities with a few clicks. The app also includes tips on keeping children safe as well as specific guidance on what to do in those first few crucial hours after a child goes missing.
However this is App presents a dilemma -- it is a great idea but if your phone is stolen or hacked, well then this data on your child/ren including where you live and some data that only a person close to your family would know may fall into other hands. I would echo what some other early reviewers of this App suggest 'a passcode would be valuable'.
You will find the App here: FBI Child ID iPhone App.