The other day I came across an old HP Journada 720 pocket computer, and had the idea to try to modernize it somehow.
The early models are pretty cheap on ebay, around $50 it seems. The early folding ones with the full keyboard, not the PDA types (those are cheaper, but who wouldn't want a keyboard?!)
I feel like it may be possible to replace the main board with a RPi Zero or some custom job. The keyboard and display are likely both standard interfaces. The touchscreen isn't anything to write home about, 640x240 resolution, 16-bit colors, and a backlight that may as well not exist, but it was brilliant in it's day.
However, in my limited searches, I haven't found any good resources or schematics.
People have hacked them to run Linux, but not truly "natively." The OS and applications are all stored in ROM, so the hack requires one to boot Windows CE (mobile Win95?) and run an executable to load the Linux kernel off a CF card. Even then it's rather slow, running off a mid '90s ~200MHz ARM CPU.
It's probably too ambitious to be completed in a week, but I figured my idea was worth sharing.
Maybe I'll try it. It would definitely be cool to revive.