Finnish cellphone giant Nokia says that it's developing technology which will allow phones to be charged via the ambient electromagnetic that surrounds all of us. Energy from Wi-Fi, phone masts, TV transmitters, and all sorts of other sources could be converted into power.

Nokia has swapped to MicroUSB chargers on its most recent handsets, including the N97, which Pocket-lint recently reviewed. However, chargers might be a thing of the past if the company's latest hopes are realised.

"Even if you are only getting microwatts, you can still harvest energy, provided your circuit is not using more power than it's receiving", says Markku Rouvala, of the Nokia Research Centre in Cambridge.

At the moment, it would take around 1,000 strong signals to pick up 50 milliwatts. An MP3 player typically uses around 100 milliwatts of power, but phones use more.

More likely in the short term is that wireless power harvesting could lengthen battery lifetimes in high-end phones, or (more likely) allow more energy usage from more features.

When will it show up in handsets? Three to four years, Rouvala reckons. The company plans to pair it with other energy-harvesting approaches, like solar cells embedded in the outer casing - a strategy recently slammed by rival Sony Ericsson.