You can type up any information that you think an EMT should know and print it on a small card. Stick it in your wallet next to your ID. It costs nothing and is every bit as effective as a roadID, dog tag, etc.

Of course, it won't have the same bling factor as a roadID bracelet or necklace, but it cheap and much easier to change the info if necessary. And you can put as much stuff down as you want.