This is excellent! I wanted this. I had noticed that Kindle had limited feature like this for certain books that support audiobooks. I had tried this style of reading with audiobook and ebook without a any automated sync, but hadn't pursued it. This looks cool. :)
Thanks! We're improving it all the time — we're working on big new releases ("v3") for the web app and mobile apps. There's a Discord server linked in the docs if you ever need any help out want to chat!