What I want is a modern Tandy 102. Back in the 80's these things were getting days or even weeks of use on a set of AA batteries. I'd love to see a modern version of this - a low power, highly constrained device (not running Linux), that runs on AA batteries. With modern components, you would think you could makes something like the 102 that lasts for months an AA batteries, but nobody has made one.

The closest things I've seen are the AlphaSmart Dana (discontinued), Apple eMate (discontinued) and the Freewrite line of devices.

I've thought about trying to make one myself from an Raspberry Pi, but those are not very low power and they seem to be tied to Linux (or at least I'm not aware of alternative operating systems).