I've been bad about carrying any kind of ID. I just forget. This is really risky because sometimes I am in towns where no one knows me and it would take a while for my spouse to track me down.

A friend of ours got me a medical alert flash drive, much like this:



In this drive I have contact numbers, temporary and permanent addresses, and all sorts of medical info as I have a couple of chronic conditions. I now leave it in my bike bag tool kit.