Apologies if this has been asked before; I searched the archives unsuccessfully, but may have used the wrong terms.

I'm wondering how useful medical ID jewelry really is. Do emergency medical personnel bother to look for it? Does it speed up their efforts if they find it? I see lots of, "This could save your life," and, "Anyone with a chronic medical condition absolutely needs to wear this at all times," online, but it all seems to come from people who sell it. Is it just marketing?

If it is desirable, what are the basic parameters for making it effective? For instance, will it be more quickly found if it's on the left wrist than elsewhere? Does it need to have a Star of Life on it, and if so does it matter what color? (It seems like wearing a blue one would be inappropriate, since I'm not identifying myself as EMS. Other than that. . .?)

In case it matters: I live in the United States and have Type II diabetes, well controlled with medication. Rapidly dropping blood sugar (which has happened a couple of times over the last few years) seems to be the most likely reason I'd need care and not be able to answer questions. Haven't ever passed out yet, but I'm aware it's a possibility.