That's pretty cool! Have you thought about making it into a PWA and ditch the proprietary ios/android ecosystems and just allow anyone with a browser to use it? It doesn't seem like there is much in this app that NEEDS to be a "mobile" specific app. It looks like you could do it all with html/js and some local storage. I'm a big believer in open crossplatform systems, when it's possible. Obviously if you need access to hardware sensors, etc, it wouldn't work very well.