I don't understand... how is registering my pets going to help them?? Do you *really* think that when someone dies, no one ever goes to their house? And, I VERY highly doubt that when someone dies, someone cross references them with the pet registry database. Do you have any links that show otherwise? i.e. I've known a LOT of people who have died. Not once did someone call up and say, "according to our database, John Doe had a cat. Is someone caring for that cat?"
However, what would be far more beneficial is to contact a neighbor you trust and ask, "if something happens to me, like I'm in a car accident and stuck in a hospital for a few weeks, could you come over and feed my cat and take in my mail?"