An interesting idea from AMBER Alert, which is the community watch equivalent for abducted children: a USB drive, made by , where you can store a whole mess of information about your child (biographical data, vital stats, relatives, places where they hang out, where they go online, etc.) in one location. Called the AMBER Alert Child ID Kit, it's $29.95, but only works for one child at a time (of course). One thing that the drive's promo page doesn't mention that I'm curious about is encryption – the information is password-protected, but is it encrypted as well? If not, given how easy it is to lose USB drives, you might be putting your child at risk by compiling this information in one place.
Update: I received an email yesterday with a press release for the Child ID Kit stating that the information is encrypted, so no need to worry on that score.