You should be able to use an electric bike motor, as long as it's the brushed type (brushless won't work). Theoretically it could output as much as its max input, about 300-400W. In practice it would only be the power your legs could muster minus a few losses. It should be easy enough to rig up mechanically, but the tricky part will be transforming that DC voltage (anywhere from 24V to 48V) into either 14V DC to charge a battery, or 120V AC to power a TV.