A new, self-contained headphone radio has solar panels on top that charge the batteries. If you prefer earbuds, you can buy an inexpensive (US$17) solar-powered radio with the panel on the radio. No more swapping batteries or charging. These radios have power all the time without action required of the user.

These products are just a small sampling of the green convenience gadgets available today. But several organizations, including Germany's Fraunhofer Institute and Japan's NTT DoCoMo have already demonstrated prototypes of the Holy Grail of green gadgets: The solar-powered cell phone. Google co-founder Sergey Brin already uses a solar-powered cell phone, according to a report in the Times of London, although details on it are not publicly available.

The all-in-one gadget of the future will be a media-playing camera phone that charges itself using whatever light is available. The addition of solar power technology will extend "talk" and "standby" times in the worst case, and eliminate charging altogether in the best case. Solar phones will be popular mainly because they'll be far more convenient.

Current generation hybrid cars, such as the Toyota Prius and Honda hybrids, are extremely popular in the U.S. in part because they're cheaper and easier to own than comparable nonhybrid cars (fewer trips to the pump).

Other companies are taking the green-is-convenient approach to the next level. Plug-in electric cars and gas-electric hybrid cars have both been around for years. Both typically charge using a special unit that must be installed in the home, and use a few dollars worth of electricity for each charge.