I just came across this interesting RF 3D imaging device from Vayyar.

A very interesting development in IC tech originally for breast cancer screening.

Walabot device - Capable of seeing though walls to find studs, piping and wiring.

This device attaches to your phone for image display and uses an array of microwave transceivers.

https://walabot.com/

https://www.newsbytesapp.com/news/science/3d-image-sensor-device-can-see-through-walls/story