The problem is that anyone acting on the info from a bracelet can’t be sure that the info is correct. Identifiers like name, address and so on can be used to get hold of medical records and then confirmation of any condition can be used to act on, but to act directly on the info on a bracelet?
What if someone puts incorrect info on the bracelet?
What if it’s not yours; maybe you wear it in memory of someone?
Blood will always be typed using a sample of your blood before you get any, unless the situation is so extreme, in which case you will get O- blood anyway.
Organ donation, at present, only takes place with the consent of your next of kin, so calling yourself an organ donor means little in a legal sense.
DNAR orders are, or should be, related to specific hospital admissions and specific circumstances and again, should be discussed with your next of kin, so writing it on a bracelet means little.
The best info is that from a verifiable medical source; best to tell your GP whatever you might be taking… 😉