I second the Yoto. My son and I have had much fun making our own cards and I got pretty good at extracting audiobooks from YouTube, processing them with audacity and making cards of book series that he was into. You can fit a staggering amount onto a single card (5hrs of audio if memory serves).

Honestly that was the biggest extra feature for us, we quickly exhausted all the Yoto store content that appealed, and weren't into any of the big franchise content (except a pleasantly surprising read of Pixar's "Cars") or joining the Yoto club.