eInk displays are really quite fun to work with. Pre-pandemic shutdown, I was working on a custom work badge holder that was primarily an eInk display to show my picture and daily work calendar.

A little Arduino can easily pull down my week's schedule from Outlook, then update the screen for the current day, then put itself in a deep (extremely low power consumption) sleep until it's time to update with the next day. Wake up, update display, go back to sleep - all in a few seconds with minimal battery use. And any time I re-sync via USB, it updates the schedule and the display, plus charges a small LiPo battery that runs things.

Is it super useful? Eh no, everything it has is on my phone already. Is it fun tech to work with? Most definitely.

PS

Probably most people know this but in case not, once you set an eInk display, it requires no power to maintain the image. I've got a few small ones I put images on a few years ago that are still just fine.