I have taken my Montclair bus tracking web site and created an App for both Android and iOS that you can download for free in their app stores.
This came about because I have been unhappy about how iOS handles progressive web apps. Every time the app is brought to the foreground, iOS does a full reload, which can be slow and annoying. The native app handles this much nicer, and doesn’t ever have to reload the state.
To build the native apps, I used this handy tool: Progress Web App Builder. It takes your website, wraps it using Cordova, and generates both an iOS and an Android project. With only a few tweaks, I was able to get them submitted to the app store.