When I was a lad, I would sprawl on the floor, reading “Dick Tracy” in the Sunday comics and marveling at high-tech police tools such as magnetic air cars and two-way wrist TVs.Nowadays an unknown policeman might saunter up to a kid in a crowd and whisper, “You’re going to ruin your posture sprawling on the floor that way. And I agree with you: your sister spends too much time showering.”According to an investigation by USA Today, at least 50 federal, state and local agencies are currently in possession of Range-R, a handheld device that uses “continuous wave radar technology” to detect motion (as slight as breathing) within a home or other building from 50 feet away. The devices were purchased without public debate and with the court system having scant knowledge of their existence.