But forget those old advertisements in Boys Life.
Scientific Blogging reports that, by establishing a grid of radio transmitters, researchers have been able to track movement behind walls using radio waves. They are not able to actually see through the walls.
Radio signal strengths between all nodes were measured as a person walked in each area. Processed radio signal strength data were displayed on a computer screen, producing a bird’s-eye-view, blob-like image of the person.
They speculate that the technology could be useful in surveillance, hostage situations, and the like.