The existence of these kind of products makes me appreciate suburbs and rural areas. I've been in areas covered in green and I've never lived a long time in a highly urban city although I regularly visit the city and things can be concerning during peak hours for traffic.
Additionally these tools give power to the people to know exactly how bad the conditions are around them which can become a great call to action because people don't normally go around measuring air pollution and when they are not sure about the pollution levels, they are unlikely to take action/sue.