If you had an accident whilst out cycling or running, do you have means of letting first responders know who you are and your emergency details? Would someone look through your jersey pockets or bags to find your ID?
Given my medical history (see previous posts) its important, no vital, that if the unthinkable does happen to me that any first responders can be made aware of my history, medication and emergency contact details as fast as possible.
Therefore, I’ve chosen to wear an engraved identification wristband, this is far more likely to be noticed before anything in your pockets.

All of my information can easily be made available to any first responder by entering my serial number and personal identification number (from the back of my wristband) onto a website or over the telephone. If the first responder cannot access the internet or telephone, at least the first two lines of the wristband will let them know my name, age and that I have a heart condition.
I’ve had my wristband and shoe IDs for over four years now, hopefully I will never need anyone to use them, but for a small annual fee I have that peace of mind that I and my medical notes can be identified at the road side.

Various companies offer these types of wristband, who you choose is entirely up to you, I got mine from RoadID.com for less than £13, including the first years subscription. When you consider the price of most cycling accessories and components it’s next to nothing.
The sport band is unobtrusive whilst riding, I don’t even notice or feel that I’m wearing it, yet it’s easily accessible to first responders.
Even if you don’t have a medical history, I strongly recommend that you have some form of easily accessible identification for first responders.