Scientists have already devised systems that allow electronic devices to scavenge power from ambient electromagnetic energy sources such as radio waves. While the technology has generally been limited to small devices such as wireless sensors, a research team has recently created a scavenging system that charges a smartphone's battery, letting it last up to 30 percent longer per charge – and the system does so using radio signals emanating from the phone itself.
Developed by scientists at The Ohio State University led by Prof. Chi-Chih Chen, one of the keys to the system is the fact that it's harvesting radio waves where they're still strong, right at their point of origin. By contrast, systems that attempt to generate electricity using whatever "diluted" waves happen to be passing through the air tend to take a long time to produce even a modest charge.
The system, which could be built into a smartphone case, works by analyzing what parts of a phone's outgoing signal aren't reaching a cell tower or Wi-Fi router – given that phones typically transmit in all directions at once in order to reach the closest tower, wherever it is, a large percentage of their signal is often wasted.
That "unused" radio signal, which is essentially a high-frequency form of alternating current, is then converted to DC and used to charge the battery. As a result, not only does the battery last longer, but there's no loss in data transmission or sound quality.
The technology is being developed through spin-off company Nikola Labs, and a crowdfunding effort is being planned to help finance production. It is estimated that the initial product, which may end up taking the form of a stick-on phone skin, will cost around US$100. The researchers would also like to find an industrial partner that could manufacture the technology directly into new phones.
Source: The Ohio State University
Sorry but they might be able to harvest some power in the lab where conditions are easy to set up but it will not translate to the real world where the phone has to find the tower and if the device is harvesting power then the phone has to up the power output to get a good signal to the tower. Such a situation would make marginal connections impossible.
Ok, not a perfect analogy, but you get my point.
If there is somehow some "excess" radiation being given off then find a way to reduce the excess, perhaps by identifying the direction to the nearest cell tower and only sending enough radio energy out in that direction. But "harvesting" the excess radiation and turning it back into electricity? stupid.
Even with data transfers phones typically download more than they upload so ideally phones don't spend that much time transmitting. Many people auto backup photos and videos but usually when connected to WiFi where the phone doesn't have to transmit at very high power to reach the wireless node anyway.
Even then I admit I am still skeptic. I think wrapping your phone in a case designed to absorb some of its transmit power would only require your phone to work harder to reach the antenna its communicating with. When your phone registers with the tower the tower probably reports its receive power to the phone so the phone can balance out its power level by transmitting with just enough power for the tower to receive it clearly without needing to transmit at excessively high power levels.
This case would essentially just create impedance (resistance) for the antenna to have to transmit hotter to overcome so there would likely be a net loss of battery life even if it seems like its recuperating something back.
Nowhere near enough to do what they're claiming it will do...
Hackaday also did a writeup on this: http://hackaday.com/2015/05/05/techcrunch-disrupt-charging-a-phone-with-its-own-transmitter/