I am the developer of the app Speech Central. The iOS version was nominated for the best accessible iOS app in 2017 on AppleVis, and macOS and iOS versions together nominated my company Labsii for the developer of the year: https://www.applevis.com/blog/closed-cast-your-votes-now-applevis-golden-apples-2017
In August 2019 the app has crossed 10,000 licenses sold on all platforms, so I've decided to celebrate this with a big discount. On 2nd September (it has already started now and may be available on 3rd September too in some time zones) the price will be reduced from 7.99$ to 0.99$.
The App Store link to get the app is: https://apps.apple.com/us/app/speech-central-text-to-speech/id1223093645