I've actually got one of these. It's not the official "Hummer" brand....but it's the exact same unit in disguise.
By shaking this thing back & forth a magnet passes through a coil and charges a battery. The light emitted is rather weak and almost pathetic, but the concept is novel.
The funny part about this thing is...well...how can I say it delicately: those versed in the masturbatorial arts will find themselves well at home...given the "motion" in which this device demands.
