This travel bag seems like something many of us could use while on a cross country road trip! Or somewhere like that?
This isn't a motorcycle specific bag, but something that's available from BoingBoing's online store.
It might look like this bag is huge but it's only 16" x 6"! What a great idea, a bag that rolls up that you can throw over your shoulder or strap to your seat if you're riding with it. It's not waterproof enough to ride through a thunderstorm but I'm sure you could find a waterproof bag for it somehow. I probably wouldn't use it for riding, but would use it as an overnight bag or weekend bag. Or if you have big cases or luggage, this could fit inside and be convenient to hold your most useful items.
For $45, I think it's a pretty cool idea. Read more about this nifty bag here.