Everyday activities — commuting to work, walking the dog, grocery shopping — could one day help keep your cell phone charged, thanks to an emerging technology that converts regular motion into power.

Boise, Idaho-based startup M2E Power announced this week it will start selling a cell-phone charger next year that can convert six hours of everyday movement (about two days of toting it around) into one hour of talk time. The company hopes to one day embed its microgenerator and a battery storage system into the cell phone itself. While motion-harvesting mobiles might not become a blockbuster hit in industrialized nations, they could fill a real need in developing nations where the power grid is woefully lacking.

Cell phones are sweeping the developing world, as the technology becomes cheap and can offer an otherwise hard-to-come-by data connection. At the beginning of the year there were a quarter of a billion cell-phone subscribers in Africa alone, according to the International Telecommunications Union. In India there are about 300 million cell-phone subscribers to date, and China has more than 550 million subscribers. As research firm Gartner notes in a recent report, the growth of the mobile phone industry “will increasingly rely on emerging markets as mature regions, such as Western Europe, Japan and North America reach saturation.”

These countries also have electrical grids that are woefully fractured, inadequate or, when actually available, intermittent. Being able to generate, store and use non-grid power to juice up a cell phone could be extremely valuable in these markets. According to the International Energy Agency and the World Bank there are roughly 1.6 billion people without access to modern electricity grids, most of them in Southeast Asia, Sub-Saharan Africa and East Asia. If motion power could give mobile phone users longer times between charging, it could be a highly sought-after feature.

In developed markets, phone makers are striving to “out-green” each other as a way to stand out from the crowd and command premium prices for their gadgets. M2E’s charger, which will sell for $20 to $40, can reduce the need to charge from the grid and thus cut down on electricity and related carbon emissions. (External power supplies, including battery chargers, make up 3 to 4 percent of U.S. electricity use, according to Ecos Consulting.) And the trend of using renewable energy to power cell phones is just starting. Solar chargers, like Solio, can power an hour of talk time with about 2.5 hours of direct sunlight.

Thus far, cell-phone companies haven’t made any moves toward adopting the technology, but they say they’re reviewing it. The world’s largest handset maker, Nokia, has been grabbing market share from competitors — selling 122 million cell phones, about one-fourth of the global total, in the second quarter — because of its success in developing nations. Its sales in Latin America and Asia-Pacific increased about 40 percent over second quarter last year. A spokesperson says Nokia is “keeping an eye out for” a variety of cleaner charging options — including power generated by human movement — that could be used in Nokia products.

Motorola sees a potential market for the battery-extending technology among users “with active lifestyles.” A spokesperson said Motorola views motion-harvesting as a viable external power source in the short term, and noted that it could become an integrated solution in the longer term, as power generation becomes an important design issue.

M2E hasn’t yet named a manufacturing partner for its charger, but the company says it is in discussions with the accessories divisions of major cell-phone companies. M2E Power’s Business Development Director Regan Rowe acknowledges that cell-phone companies see an early-adopter risk in embedding the technology on the phones themselves, so the external charger has been the company’s first step to commercialization.

Ultimately, the determining factor in whether motion-harvesting technology makes it into mass-market cell phones and accessories will be cost. How much will it cost to add the technology to phones, and how much is the user willing to pay? If the price tag remains high, the technology could end up as a pricey feature on a high-end green phone, rather than solving energy (and digital access) issues in the developing world. But if the cost comes down enough, it could be a real game-changer for cell phones with sporadic or no access to the power grid.

This article originally appeared on BusinessWeek.com.