I built an app that shows the air pollution levels in Hong Kong based on Western standards, primarily because I couldn't understand the local governments rather lax air quality index. I'll probably never recoup the development costs or even the server expense, but I didn't think it would be right to charge for it. In a heavily polluted place, some folks with asthma and respiratory problems or even young children simply shouldn't go out on certain days.
http://itunes.apple.com/us/app/hong-kong-air-pollution/id504...