Stupid question as someone who worked on wifi for many many years: What is the point of this? How is this remotely useful? There are tons of better technologies to use?

Let me guess, this thing puts the wifi into some constant transmit mode and measures loss rates as it passes through objects, and scans in some pattern, measuring loss rates at the other side.

Is this just packet based radar? Is this a cute way of saying "using the 5GHz band to scan through walls when you have a receiver on the other side of your object"?

Here's the thing: different materials absorb / reflect radio waves with different characteristics. You could just as easily make these letters out of a completely different material that doesn't remotely resemble a letter and it could look exactly like a letter.

How is this useful? And why is wifi the medium to do it. You can't just do this with a regular old driver. Your normal driver will be selecting antennas, adjusting rates for loss rates. This is clearly a dedicated radio with some open source driver that they've hacked to do this.

Ugh. This just seems like a dumb waste of time. This isn't even a passive radar, as it requires there to be a receiver on the other side. There is no bouncing back of signals.

"It does not require any prior RF data for training a machine learning system for RF sensing." Yes, but it does require very specific material characteristics that it is trying to detect at fixed distances. Namely edge keller cones on specific materials, and hoping that other materials don't replicate similar patterns.