No batteries required - I have the Wi-Fi Power!
It sounds like something out of science fiction, but the reality of wireless power maybe getting closer that you think, the concept of devices that can "capture" power from a wireless signal have been challenging the brain of the best engineers for years. However now a group of research engineers have created a new technology they call "Ambient Backscatter".
In short the technology uses the power of existing wireless signals in the air such as from a TV mast and then transforms these signals into its own communications medium. Taking the power required from the signal itself. The result? Two battery free devices are able to communicate with each other effectively forming a network out of thin air. The data rates are slow at the moment - in the realm of 1 kilobits per second – but with the primary market seen for telemetry of data from sensors, this is enough bandwidth to send sensor readings, text messages and contact information.
A company in Mountain View California www.powerbeaminc.com has taken the next step and has products for the consumer market which are truly wireless. At the moment the power levels that has be transmitted are limited, but are enough to power speakers, digital photo frames and other low consumption devices. The power is transmitted by laser diodes, and the receiver is a photovoltaic cell – effectively a highly efficient solar cell.
The market is moving forward at such a pace now that the "Wireless Power Consortium" has been formed to create standards for this new technology. What seemed like science fiction a few years ago is rapidly becoming a reality, and the market will continue to grow in coming years. Just this year Aerohive produced an April Fools video in which they talking about "Electrohive" wireless power. I tried to find the video for you all to see, but all traces of it have been removed from the web. Maybe they too have realised that wireless power is moving out of the realms of star trek and into our homes and offices?