The most useful camera for secretive spying is shown in the 'How to See Around Corners' video. Scientists from MIT, Harvard and Rice University have successfully built a camera that can put together an image of an object not directly within its line of sight.
The camera works with laser bursts. It shoots photons at whatever is straight ahead, and when the photons reach said surface, they scatter into even more photons traveling in all directions. Some of these photons are bound to reach the object that the camera is trying to see, and once they hit the object, the photons scatter again to travel back to the camera lens. The camera then measures how far apart the photons that reach it were, and submits the information to an algorithm that uses the differences in time and distance to render an image of what could be around the corner. The 'How to See Around Corners' video provides this information alongside a digital demo to ease the understanding of the camera's working. This camera can be used to aid firefighters and police officers in navigational purposes and even be used in medical devices.