From the DARPA website on project Revolutionary Enhancement of Visibility by Exploiting Active Light-fields (REVEAL) program
Imagine, for example, squad members patrolling a street in a deployed urban environment, and an armed assailant crouching behind a car or a concrete barrier. Without the benefit of different vantage points (from the air, for example), the squad could be blind to the hidden threat. If by chance a glass storefront window were behind the assailant, the squad might spot the assailant’s reflection in the window. But if the backdrop were a brick wall, there would be no visible reflection. By exploiting currently untapped aspects of light and the varied paths of photons bouncing off the brick wall, troops using hardware based on the theoretical foundations provided by REVEAL might someday be able to detect the otherwise hidden assailant [or see clearly what people are doing inside their homes].
Another potential application could be determining an unknown material’s composition and other properties from a safe distance, avoiding the potential danger associated with close proximity and physical examination. Based on information carried by the photons interacting with the material, it may be possible for troops in the future to identify radioactive, biological or chemical threats and camouflaged targets from much farther away than currently possible.