First, before I go into detail about how the Seiko watch works or how to apply that to the truck we should become familiar with how electricity is generated in the first place. Basically a magnetic field is needed and a loop of wire called an armiture is needed. The magnets should be arranged on either side of the armiture, as long as opposite magnets are on opposite sides of the armiture. When the armiture is rotated between these magnets it will induce a current. This current can be transfered from the armiture to a battery or directly to an electric motor.
The Seiko watch uses a very small generator to keep its battery charged. The generator is run by the movement of a weighted pendulum, which is moved by you. When you walk your arm swings and when you arm swings the pendulum swings and when the pundulum swings a tiny bit of electricity is generated and sent to the battery. A fully charged battery will last up to about six months.
Now we take the watch technology of being powered through movement and stir it in with the principles of generating electricity and stick it into the truck. But where? In the axles or in the wheels. You simply line the inside of the axles with magnetic strips. Positive on one side and negative on the other. Then put wires up and down the axle lengthwise to cut across the magnetic feilds. Then when you start driving, presto, electricity is generated. In an electric car this could be linked to the battery and charge it while you drive.