A quick search for “traffic sensor” returns a whole class of items that all basically look like the rectangular brick in your photo. Supported by the temporary / construction look of the one in the other comment.

Construction company puts in a lane restriction or other traffic modification, plop down a traffic sensor to make sure cars are still flowing through properly.

Maybe some utility in a broadcast device of some sort that puts out a “cloud” of white noise in the wifi bandwidth. It’ll stick out like a sore thumb that the detection is being tampered with, and will probably disrupt wifi in an area, but providing too much data for the system is probably a better call than trying to hide yourself from it.

There’s just no feasible way right now to stop the way that radio waves interact with your body, other than not being in that location.

From reading the article, not to my understanding. This technology uses the way radio waves, in this case wifi, are bouncing around a space in order to build a picture of the people in it. These clothes just block the signals from devices underneath them. As far as I know, the shape of the garment (and therefore you) would still look the same, and then whatever recognition, gait analysis, etc would still work.