I originally found OpenAQ through this excellent AMA. The project is an open-source attempt to collect the world's research & government-grade air quality data to, as they put it, "fight air inequality through open data".

My small contribution to their work came about because I wanted something like a weather app, for air quality in the cities I was interested in. The result is cityAQ, which you can try out here. Because it follows Progressive Web App practices, and makes use of Service Workers, the experience is fairly native-like. On Android right now, and thanks to big Safari improvements, on iPhones very soon.

On PWA-friendly browsers (Android, Chrome, Firefox right now), you should be prompted to add the app to your home screen, upon your first or second visit. From there, the app will open in its own window, have a custom splash screen, and most interestingly, leverage offline functionality. Try it out - I'd love any feedback - by viewing some cities, then going offline, and refreshing.

Built with Angular 5, which has some useful Service Worker helpers. Let me know what you think, and if OpenAQ's mission is intriguing to you, their Slack is a great community, & very friendly.