While there are many devices that after a few hours in the sun are recharged and ready to use, there are also a few that can be used when that sun is difficult to find. For several years now I've seen some radios and lights that can be cranked in order to charge the power supply and are gret for use in emergencies.
If you search online for "no battery radio," you will find several that can either be charged in the sun or have a wind-up recharge. I even saw one that features a radio, a light, a siren (for attracting attention in an emergency) and an outlet that can charge a cell phone. What a great idea for a camper too!
Next to solar and wind power a little "elbow power" is a great thing.