Always carry your identification card. In an accident, your I.D. card will tell the people helping you that you have a pacemaker. Your card can be particularly handy if you travel by air. The metal-detection devices in airports may detect the metal in your pacemaker, although they won't damage it. Showing your card may save you some inconvenience.
The Pacemaker Wallet Identification Card is available as a PDF. Print it out and carry it with you.