We already are.
"Giving Transportation Security Administration agents a peek under your clothes may soon be a practice that goes well beyond airport checkpoints. Newly uncovered documents show that as early as 2006, the Department of Homeland Security has been planning pilot programs to deploy mobile scanning units that can be set up at public events and in train stations, along with mobile x-ray vans capable of scanning pedestrians on city streets.
The non-profit Electronic Privacy Information Center (EPIC) on Wednesday published documents it obtained from the Department of Homeland Security showing that from 2006 to 2008 the agency planned a study of of new anti-terrorism technologies that EPIC believes raise serious privacy concerns. The projects range from what the DHS describes as “a walk through x-ray screening system that could be deployed at entrances to special events or other points of interest” to “covert inspection of moving subjects” employing the same backscatter imaging technology currently used in American airports...
...In August of last year, Joe Reiss, the vice president of marketing of security contractor American Sciences & Engineering told me in an interview that the company had sold more than 500 of its backscatter x-ray vans to governments around the world, including some deployed in the U.S. Those vans are capable of scanning people, the inside of cars and even the internals of some buildings while rolling down public streets. The company claims that its systems’ “primary purpose is to image vehicles and their contents,” and that “the system cannot be used to identify an individual, or the race, sex or age of the person.” But Reiss admitted that the van scans do penetrate clothing, and EPIC president Marc Rotenberg called them “one of the most intrusive technologies conceivable.”"