aqicn.org is an excellent website for getting smog (air quality) data for cities around the world. I highly recommend using their existing websites and apps!

This app is an unofficial wrapper around one of their APIs, which enables your Pebble to get an air-quality reading. That way you'll know how much pollution you're in for without even looking at your phone!

Controls:

Up/Down: switch between cities.
Select: view attribution (where the data came from)

Many thanks to aqicn.org!! To update the list of cities, visit http://aqicn.org/city/all/ to find valid city names.

Currently only tested on Pebble Time Steel