[sgirard]

I would love to be able to image elements inside a wall cavity: studs, pipes, ductwork, electrical lines. I don't know if it's possible with this technique, but maybe someday these ideas will lead to something like an x-ray for building structures.

[kenhwang]

You're describing a modern off the shelf studfinder. Those already use magnets, radar, and ultrasound to detect studs, pipes, and wires.

[gweinberg]

I've got a stud detector and it works like crap. But it's pretty old, maybe new ones are better.