Personally, I would be more inclined to push for ID cards, which can more specifically identify the person it is issued to, as well as the specifics of the medical condition and terms of the DNR order. A small laminated ID card with a neck chain would suit the purpose well. And, being as it would be around the neck, it is much less likely to be overlooked than a bracelet on the wrist.
Excellent idea but not always practical for the confused nursing home or hospital patient who is always taking off their clothes and whatever other accessories. Even when they are not confused it could come off with their clothes unless it was sturdy and short with a strong clasp.