The OLPC project has investigated various human-powered chargers for their low power computer for children. Perhaps one option would be a pendulum generator.
Automatic quartz watches have a miniature electrical generator. As the wearer moves their arm, a pendulum swings and this is used to generate electricity to charge a battery. These units have the disadvantage of needing a heavy pendulum and complex gears to connect the generator.
Something simpler than the watch generator, on a larger scale, could be made from a brushless electric motor. These have a set of rotating magnets and stationary coils of wire. Spinning the shaft of the motor operates it in reverse, generating electricity. If half magnets were removed, this would unbalance the motor, making a pendulum.
Such a unit might be made carried in a pocket, handbag, briefcase or backpack. It could be built into a notebook computer, in the space normally used by a CD-ROM drive, hard disk or PC-Card.
A pendulum generator might be built into a mobile phone or the battery of the phone. many phone already contain a vibrating alert, with a small electric motorwith an unbalanced weight on the shaft. Rotating the weight make the phone vibrate. The pendulum generator could double as the vibrating alert.