[evan_au]

The Gravity Light has a couple of electrical terminals on the front so you can connect other devices, like a low-power radio receiver.

For the remote regions Gravity Light are targeting, batteries are unaffordable, whether disposable or solar cells driving a rechargeable battery.
While the cost of a battery may not be an issue for Westerners, unused batteries must be checked regularly or they will corrode, and rechargeables need to be kept charged. So this bypasses the battery problem.

[RE.Craig]

No, I am not talking about some miracle energy device, I am talking about pulling up a mass and letting it drop (slowly with the help of gears) to run a generator.

Has anyone here seen anything like this to operate, say, a small radio?

I remember seeing a WW2 Japanese emergency radio beacon that used a weight and pulley clockwork drive. It was standard issue on their big bombers. If one went down and the crew survived they would set up the radio beacon on it's tripod and set the pulley in action the radio would then transmit an emergency signal. The Americans and British were not so lucky as they had to continuously in turns hand crank a radio attached to a dynamo. Not a nice job in tropical heat!!!

[syhprum]

According to some correspondents there are magic gearboxes available that output much more power than you put in , they use them in clockwork cars !.
Crystal radios might seem harmless but in fact they cause a lot of interference by cross modulation , I remember a neighbour complaining bitterly during the war that my radio was inflicting the "Voice of America" on him while he was trying to listen to the "home Service"