I keep medical history on a small piece of paper covered with scotch tape in my wallet. It has come in handy in the past year. I have been to the doctor alot. When the doc wants to know what I am taking I can just whip it out.
Last year I had my colon removed as a result of ulcerative colitis that would not respond to medication. So, I kinda want that info to be available to and EMT etc.
I don't think I will put one in my PSK. I don't think anyone would think to look there. They would probably take one look at it and say "What the hell is this?"