This looks super fun!
Lately I've been dreaming of building a credit-card sized computer (thickness included) using a e-ink display and ultrathin battery. I haven't found a good purpose for it though.
Speaking of E-Ink, if you remember the "Thinkpad X230 with “e-Ink” display at 30fps": https://news.ycombinator.com/item?id=26860609, I'm selling two of them: https://www.ebay.com/itm/255123140172