There's a new how-to over on the Instructables website you might want to see. One ambitious Kobo owner shows you how he voided his warranty (and possibly wrecked his device).
He mounted a pair of solar panels on the back of his Kobo. I'm all for solar power, but I really think they should have been mounted elsewhere - built into a case, perhaps?
I'd prefer a case because there are a couple problems with the design. the first is that you can't use the ebook reader while charging (unless you're lying on your back). The panels are mounted on the underside of the Kobo, which means they'll also see a greater amount of wear and tear.
Still, in a crazy sort of way it is interesting.