I feel like e-ink displays/EPDs are widely used, but underexplored, by major manufacturers at least. The person behind the Modos project already linked by someone else has put a lot of effort into pushing EPDs to their limits and put together the best technical documentation for EPDs that I know of: https://github.com/Modos-Labs/Glider

EDIT: Here's an older demo of theirs: https://www.youtube.com/watch?v=XduK7wn9SE4