The city council of Salford, Lancashire, UK printed these wallet "right-to-die" cards. They're freely available in pubs, banks, hospitals, libraries, and other public places. They're sort of like a living will combined with an organ donor card. If you don't have the mental capacity to tell doctors how far they should go to save your life, this card lets them know you've already planned ahead for just such a situation. From the BBC News:
…Its backers say it is a practical way of implementing the Mental Capacity Act, which came into force in 2007.
The act allows adults to draw up "advance directives" stating what sort of treatment they don't want should they lose capacity. They build on the principle of "living wills" but, crucially, mean that doctors are legally bound to abide by a patient's wish to refuse life-sustaining treatment.
Carrying the card alerts anyone who finds it that the patient has made decisions about treatment, and there is a detailed statement to be found with named relatives or friends and, ideally, their GP.