Well, I'll chime in with the others who are first responders (I am a firefighter/CFR, working to EMT soon) and I'll agree with the bracelet as the most important thing for serious medical conditions (like diabetes).

As far as ID and alerts and medical info tags let me be a little gloomy here and remind you that in a trauma first response situation, I don't care what your name is, I don't care where you live, I don't care what your religion is. I'm going to get you out of the car wreck as fast as I can, and I'm going to try not to hurt you while doing it. Once you're out of the wreck, I'm going to do the minimal necessary treatment to hold you together until you get to the hospital or until someone with more skills than me takes over.

OK, so that's first reponse in a nutshell. But what about ID for a kid? Well that's a bit of a scary issue - your kid is riding with a freind, they get into a wreck...who's kid is it? It's easy to imagine and it does happen. However, the reality is that it's not too hard to locate parents in that situation, they come forward fast enough.

Finally, a thought on the process of fingerprinting and photographing your kids. I see this at couny fairs and festivals, and wonder if anyone stops to think what the purpose of this process is. Basically, it's for body identification, nothing more. Fingerprints on file do nothing to prevent abductions. On the other hand, a photograph of your kid that was taken 3 years ago is pobobly useless. Now, having been involved in a lost child search for a freind's 9 year old daughter a couple of years ago, I can tell you that a RECENT photo is very much needed in that situation. That's why when we go to places that are big and crowded, I take a picture of my kids (and their shoes) with my cell phone camera before we go in. It cant' get more recent than that. Sorry, I've wondered a bit. It's early I haven't had coffee yet.