According to the Technology Review published by M.I.T, researchers at the University of Utah are on their way in developing internet wireless abilities to see through walls. The technique, formally known as variance-based radio tomographic imaging, utilizes radio signals from Wi-fi networks in order to process signals that would indicate movement through the particular wall. In simpler terms, the radio signals from wi-fi networks can be manipulated to detect movement through walls due to a change in volume of space.

Still confused? Most people often are but the researchers are unfazed and are moving forward in their attempt to defy yet another, law of physical property.

Source: http://www.technologyreview.com/blog/arxiv/24193/