I made my own wearable computer with a Raspberry Pi, and it was almost too easy

Except for the 'wear' part, or use while wearing, or software and applications. But--small battery-powered computer usable in class with slightly more hacker aplomb than a cellphone with BT keyboard: Check.

It'll be interesting to see if anything more comes of this--the easy part is done. Personally, I would have at least opted for a one-hand chordic keyboard and a display you can use while walking.