A few of these, updating them maybe once a day, would be excellent.
Also for outdoor advertisement. Replacing those LED backlight. Unfortunately the video has shown the quality isn't anywhere near good enough. PPI and colour accuracy are too low.
The dream of someday coding on a high-resolution decent-refresh-rate color e-paper monitor is still alive!
Digital photo frames that cycle throughout the day, dynamic posters and murals with art that changes with the time or viewer, refreshing price labels, clocks with minute resolution, data visualization over large time intervals, informational displays...
You might not even have to paint the entire screen at once, but can perhaps update only the dirty regions.
Not everything needs to display video or respond in real time to human input. There's so much painted in the world around us that could have value added by letting it refresh on the day, hour, or minute.
(Computer vision would be cool though, imagine if it was different every time you left and re-entered a room?)
That said, you could probably put a one-cell LCD (like those shadeable windows on the 787) over the screen to black it out during the update.
Also interesting that the iMac doesn't have TrueTone, so he had to do the white-balance matching himself.
Honestly I'd say this is possible now. Modern two-color (usually black/red) e-paper panels can refresh at 5-10hz. Grayscale only panels can go even faster, but it's not a huge problem for text. My e-reader gets around 100 hours of battery life but drops under 10 if I enable wifi and any lighting. That's running a lightly modified android. I'd imagine a dedicated os just for text and vpn/git could do quite well. Currently the only players in the big e-paper market are going for ereader or "sketchbook" markets.