While we're on self-powered devices, how about a scanner with optical character recognition that ships with a bag of mulch and some baby worms, and when you scan the documents for your computer, it shreds the paper and makes a compost heap, burning off the generated methane for electricity? You'd rip out the pages out of books as you read, feeding them one-by-one to the scanner which would liberate the letters from the ink as it consumed them.