It'd be cool to take the kind of modern low-power electronics that go into devices that manage to get a few hours with a tiny 40 mAh or 150 mAh battery, and just hook them up to a modern phone or laptop battery.
I feel like you could reasonably make a useful computer that could be left on for an entire week before it needs a charge, if you accept having a not-great screen.
@NovaSquirrel yes and no.
If you eschew web browsers and video playback, go back to stuff we had pretty well handled in, like, 2001. (Native apps doing email/calendar/chat/etc.)
Grab an appropriately "underpowered" CPU.
Apply modern power saving, sleeping, and application management.
You'd go a long way.
But the only low power display I can think of would be the old non-backlit monochrome LCD. And frankly I wouldn't wish that on anyone.
@astraluma @NovaSquirrel any reason you wouldn't consider e-ink as an alternative display method?
@elfi @NovaSquirrel it depends a lot on the usage pattern.
eInk takes no energy when the display is static. This works very well for an eReader--the device can go into deep sleep (~off) between page flips, which is a pretty much the entirety of the device's life. This falls squarely in the original post's premise.
But refreshes on eInk are expensive, both in time and in energy. For a general purpose computer, the time between interactions is much harder to predict, and there probably exist usage patterns that completely wash out eInk's static energy savings.
A single animated gif almost certainly falls under this category.
@astraluma @NovaSquirrel oh yeah, certainly
Admittedly I do have some fond memories of old palm pilot LCDs, especially with the backlight. Pretty glowy green lämp~
@astraluma @NovaSquirrel now I wonder how much life you could get out of a workhorse machine with productivity suites and cellular internet but monochrome LCDs...