How good is the health care where you're travelling? In some countries, you can count on good care anywhere; in others, you're fine if you stick to a big city but really don't want to have an emergency out in the boonies.
This Health Risk Map, prepared by International SOS, rates countries on the state of their medical systems. They're a company that provides emergency medical services for corporations, so they focus on whether they would choose to evacuate you or bring you to a local hospital. Still, the map can be useful as a tool for planning travel: just how risky would it be to get seriously sick or injured in your vacation spot?
Some countries don't fall into an easy category: there may be a huge difference in care between urban and rural areas, or between public and private hospital systems. Those countries are shown in brown on the map, and some are explained in more detail in this interview with NPR. Check out the link below for the full map.