My daughter was walking through WTMD at CPH when it beeped ("randomly" according to the agent there). So, she was required to stand in front of the machine on the rubber mat (with foot marks) and spin around, while a screen next to her showed the progress of her turn, and finally turned green.
It looked like some sort of scanner, but it only had a single vertical surface on the side (where the screen is installed) and a rubber mat underneath. I wonder what technology is that?

Oh, she was still patted down afterwards.