A simple debit card or drivers licence is good enough, an ‘incase of emergency’ sticker on the phone would probably help speed up the process of identifying you, but wouldn’t help an ambulance… the key thing is being found.
If you come a cropper in the middle of nowhere, the most important thing is getting an ambulance out.
That relies on passers-by stopping and raising the alarm.
Above that you’re looking at GPS beacons, which cost, or letting people close to you know your route and checking in with them.