A simple and good idea: The SOS Coin. A round plastic disc that you can attach to your laces (like a ChampionChip). On this disc you can have you personal data printed!
Of course every runner thinks he will return savely home when he goes out for a run but you'll never know. Maybe a cardriver is not paying to much attention of you get disorientated by becoming too cold or tget overheated in summer and you will not be able to express yourself properly. Than this little disc with your address or the phonenumber from your homefront can help! You yourself can decide which information it should contain. Do you have key medical information? Add it to the coin.

Of course you could carry an ID card, actually in the Netherlands everybody above 14 is obliged to ID himself when requested by the police but be frank:"Do you carry an ID card when you go running?" I don't!
An alterantive I came across a few years ago was the following: Take an old plastic membership card which contains you address. Cut out the address, punch a hole and attach this to your laces. Of course this is just your address and not the contact details form your homefront! Therefore: A simple and good idea this SOS Coin.