saying pixel Qi "displays" were around or available is an overstatement. For a short while you could pick up the screen as a hacker kit. Just the glass and ribbon cable. It wouldn't be clear to build a housing and then make it run via USB, which is really the best way to use as a portable secondary monitor if you think about it. That and the screen quality was never really good. Dark mode was really silvery. I had the OLPC with the pixel qi screen and it was neither good as either screen, lit or not. Sadly they never became anything for the consumer. I'm not sure why either because they claimed they were in this great niche where they could pump out a lot of product because their build process was right inline with LCDs except for minor tweaks.

If you want to say they've existed you they have since maybe 2005 / 2006. Doesn't mean they have been accessible to anyone for mainstream use. This chnese e-ink display could get traction but they need to cut the price in half. the best innovation on e-ink lately is the yotaphone. Makes the most sense, solves problems and is accessible in price.