Apparently, Heathrow airport is 'testing' this technique. Here's Peter Foster, Telegraph's India correspondent, on his experience -- in a post titled "Butt-naked at Heathrow":
I was directed to remove my shoes and then enter a booth where, at the instruction of the official, I placed my feet on the patches indicated on the floor.
One after the other I struck three rather awkward poses, hands reaching for the sky as if trying save a Beckham free-kick curling its way first into the top right corner, and then the top left corner.
The whole procedure took a minute at most and it was with some curiosity that I skipped round to the back of the booth to where a technician was reviewing my scan behind a small curtain.
Well. There's no polite way of putting this. There I was, on screen, absolutely butt-naked. [...]