That's awesome! I have plans to do the same thing but for android.

How long did it take you to implement this proof of concept?

Thanks for your comment. Let me know if you end up implementing this on Android. I think this concept could be adaptable to other platforms or languages. I just happened to be working in Swift and so I started there.

It took about a week to prove the idea was viable and then another week or two to get the code into a state where I felt it would be useful to share.

I am a native Android developer and decided to focus only on this platform for now, as I had no desire to mess with Electron and other web frameworks.

Any existing iOS alternatives with similar functionality?

The closest alternative, which offers only text-to-speech mode, is Speechify. However, they charge over $100 per year, which is significant. A lifetime license for Quickify is available for just $39, or $1.99 per month.

I don't want to seem assuming, but I haven't seen such a set of features in any application yet, really.