An unusual portable 13.3” e-ink display. Weighs about 1.5lbs, connects to computer via HDMI. It’s small/light enough that it can sit in front of my normal MacBook Pro display when the computer’s open in my lap.
It’s a bit fiddly: there are lots of contrast settings and update speed settings, and I find myself constantly wanting to adjust them. While it’s nominally 2200x1650, macOS is unusable at that resolution. 1344x1008 and 1280x960 are more plausible functional resolutions, though of course those are a bit cramped. (n.b. a 13” rMBP is only 1280 points wide!)
Once set up, it’s surprisingly responsive. It’s not exactly sharp, which does damage the pleasure of writing/editing/coding/etc, but it’s not unusable either. You can optionally get improved sharpness in exchange for slower refresh rates.
It’s quite expensive: about $1000. It’s less suitable for use at a desk: you’d really need to supply your own VESA stand.
It has no internal battery or system—it’s just driven by your computer. It’s powered via USB. Because it’s e-ink, the impact on battery life is presumably fairly low: I measure 0.2A, which is 1W at USB’s 5V. My MBP has a 100Wh battery, so this is a pretty negligible impact. An afternoon of use would consume a marginal 5%. And the internal display’s backlight consumes much more than that, so you’re going to get better net performance from the display swap alone. But connecting an external display requires using the discrete graphics card, which has a much larger impact.