Researchers at Stanford University have developed a laser that shoots photons from any tiny hole such as a keyhole that can expose everything inside a room from the outside without even opening a door.
Once the photons have been fired, they reflect off of a surface on the other side of the room such as a wall. The sensor is able to record the time delay of the light that returns. This data is then processed to reveal a graph in 3D in order to distinguish objects and contents that are inside the room.
This has been developed for scenarios such as in the event of a building collapse and aiding in finding survivors, or perhaps even in a hostage situation to gather as much information as possible about the environment. Furthermore, this may also be used in the event that there might be a death or emergency in an apartment building.
Take a look at the video below by the YouTube channel: Later Clips on This Laser Can Expose Everything Inside A Room...