In 2012, i’ve developed the iSPEX iPhone app for Leiden University. With a tiny spectro/polarimeter-add on, you can determine air pollution by sweeping the iPhone to the daytime sky. Thousands of people contributed to science during 2 days of measurement. You can read more on the iSPEX website.
With the dark sky meter you can measure light pollution at night. If you use both apps and own the required optical add on for measuring air pollution you are all set! During daytime you can investigate the air quality and see how it impacts light pollution for example. Do your own research with your own optical laboratory: the iPhone.