AD wrote a post recently about having to break into a home in order to get to the person who had requested his assistance. He offered several ways to help emergency services folks find and get to you. He made very good points, and I agree with all of his suggestions, save one.
One of his ideas was to leave a spare key somewhere outside, and have the 911 database updated to include this information. I see potential problems with this. Perhaps my risk to reward assessment would be different if I were sixty years older and much more frail. However, I see the chances of either abuse of this information by government officials or compromise of the database as much more likely than me fucking myself up so badly that I can’t make it to the door after summoning EMS.
Just my two cents. Your mileage may vary.