I know your comment was tongue-in-cheek, but honestly how difficult would it be to make a device charger powered by a clockwork mechanism? Those AM/FM/Shortwave radios made by C. Crane are wind up and have been around for 20 years. Some come with flashlights and USB chargers built in. So how hard would it be to make a charger or even the device itself wind up?
Just thinking out loud.
CC
Anything and everything is possible, the question is how useful. The wind up battery radios, for example, would give a 450 maH battery a recharge. The typical cell phone battery has 2300 maH batteries (can be as large as 3200 maH.) So if it took ten minutes to charge the radio, it would take about an hour to charge a typical cell phone. That’s a little bit more than most people would be willing to invest into the process.
Alternately, you could use a dynamo mounted on a bike to run a converter to recharge multiple devices at once.