The short answer is: scientifically yes, but practically no…

The short answer is: scientifically yes, but practically no. You cannot use a standard router to "see" inside a house like a camera would. However, there is a field of technology called Wi-Fi Sensing that uses radio waves to map environments and detect movement.

How "Wi-Fi Seeing" Works
Think of your Wi-Fi router like a lighthouse that flashes invisible light thousands of times per second. These waves don't just go to your phone; they bounce off walls, furniture, and human bodies.
Signal Disturbance: Every time you move, you disturb the Wi-Fi signal pattern.
CSI (Channel State Information): Advanced software can analyze these tiny "glitches" or changes in the signal.
AI Reconstruction: Using Artificial Intelligence, researchers can translate these disturbances into shapes.
What can actually be "seen"?
It is important to clarify that this is not "video." You won't see colors, faces, or clothing. Instead, the technology generates:
Heatmaps: Showing where a person is located in a room.
Wireframe models: Researchers (such as those at Carnegie Mellon University) have used Wi-Fi to create 3D "stick figure" versions of people through walls.
Vital signs: Some systems are sensitive enough to detect the rising and falling of a chest to monitor breathing rates without sensors.
Is someone spying on you right now?
Highly unlikely. Here is why you shouldn't worry today:
Complexity: It requires specialized algorithms and high-level data processing that standard consumer routers aren't running.
Resolution: The "images" are very blurry. It’s more like seeing a shadow through a frosted glass window than looking through a camera.
Hardware: Most current routers are optimized for data, not sensing. However, the upcoming IEEE 802.11bf standard (Wi-Fi 7/8 era) is being designed to make "Wi-Fi Sensing" a built-in feature for home automation.

Future Use Cases
In the next few years, this won't be used for "spying," but for:
Elderly care: Detecting if someone has fallen without using intrusive cameras.
Security: An alarm system that "feels" a person entering a room.
Energy saving: Turning off lights or AC when the Wi-Fi senses the room is empty.
Would you like me to find more technical details on the 802.11bf standard and how it will handle privacy?