DigiAcademy is (was?) an app that allows a content owner to make available their content to their customers on mobile devices. The app is unmaintained since 2019 and may be soon removed from app stores.

DigiAcademy supports 3 types of content: audiobooks (online and offline), books in pdf format and courses using a subset of HTML. The courses and audiobooks are split in chapters. Multiple playing speeds are available for audiobooks.

This project had two technical challenges: the audio playback part, which needed to work well for both online and offline content, on both iOS and Android. The second challenge was media management, I wrote about it here: https://www.photostovis.org/blog/2016/01/17/why-fizzbuzz-matters/.