At first I thought it was something attached to your hiking stick, but leaving it in backpack there's no way it'll generate anything useful at all. Anybody with a shake light knows even with the best quality material you'll have to shake like mad to get a 5mm LED to work a few minutes, let alone charging electronics from movement of a backpack.

Plus when you read their website they crammed a whole bunch of jargons in their explanation on how it works, making a simple to understand concept much harder than it is. Usually a sign of crap product.