Reevu Rear-View Motorcycle Helmet
This seems like an obviously good thing: a motorcycle helmet from Reevu that provides the same kind of rear-view-mirror experience as a car, just off-sight enough to be out of the way but keep your attention if something's there. And since it was on Engadget, I assumed it was electronic, using a camera and a small LCD. But no! It's all mechanical - more like an old-school periscope than the rear-view cameras found in luxury SUVs. And somehow, that just makes it even better - robust, pure, no batteries required. And, of course, safe - and very, very useful!