Dear sjm: you reminded me of the little generator on my beloved Raleigh bike, how little drag it caused when riding at night with it on. And the same technology over fifty years ago made possible a real "flash" light that I saw one night down on the Cape Cod canal, where I was fishing. A guy came along with a hand held light, that when he squeezed the handle turned a tiny generator with enough flywheel effect to give three of four seconds of bright light, and only a little longer wait before he could squeeze the handle again. I didn't get a chance to ask him the name of the manufacturer. I have never seen one since.