The FBI joined the booming mobile phone app market on Friday with the launch of a tool to help parents find missing kids.\"You\'re shopping at the mall with your children when one of them suddenly disappears. A quick search of the nearby area is unsuccessful. What do you do?\" the promotional blurb for the application says.The answer? If you have the free FBI app -- which is only available for iPhones at the moment -- and stored photos and vital information about your children on it, the data you need to be reunited with your missing child would be \"literally right at hand.\"Parents using the app \"can show the pictures and provide physical identifiers such as height and weight to security or police officers on the spot\" or email the key information to the authorities using a special tab on the app in the event their child goes missing. According to the Federal Bureau of Investigation, a child goes missing in the United States every 40 seconds, and \"many never return home.\"The FBI has plans to expand the app for use on other mobile devices, and to add more features.