Nokia is planning to use electromagnetic waves to generate electricity that can be used to power up the mobile device for longer talk time without the need of recharging.
In its famous Research Centre in UK they have been working on a prototype for some time now. This prototype is able to convert the ambient electromagnetic radiation from phone antenna or other source to electricity. It is also expected to detect and convert waves from other radiation sources like cordless phones and wifi devices in its surrounding.
Currently the output is about 3 to 5 miliwatts which is only a tenth of required 50 miliwatts target required to sustain the device in normal operation. Noka predicts that it would be able to achieve that target within the next 3 to 4 years