Snooping is big business these days, especially if you belong to the security services (or if you're David Cameron). But US police have dived headfirst into the realms of sci-fi with today's revelation that they have been using radar devices which allow them to "look through the walls" of anybody's home. And if that sounds suitably dystopic to you, how about this: they've been doing it on the sly for the last two years. 

USA Today reports that 50 American law enforcement agencies have used the Range-R, a device that uses radio waves to detect if anybody is inside a house and where they are. The machine is so sensitive that it can sense human breathing from a distance of more than 50 feet. The controversial form of detection is known as Doppler radar. 

The technology is potentially in breach of the law. The US Supreme Court views these kinds of devices are illegal without a search warrant, although it's currently unclear whether their usage is a breach of the Fourth Amendment.

The Range-R was first used in Iraq and Afghanistan, but people are understandably concerned that war technology is transitioning seamlessly from international conflict into domestic police work – especially amidst concerns voiced by the American public during Ferguson protests that the police were becoming a fully-fledged militarised unit.

Human rights organisations like the American Civil Liberties Union (ACLU) believe that the devices set a dangerous precedent. "The idea that the government can send signals through the wall of your house to figure out what's inside is problematic", ACLU principal technologist Christopher Soghoian said. "Technologies that allow the police to look inside of a home are among the intrusive tools that police have."

If you're wanted by the feds in America, it might be worth staying indoors and remaining totally motionless – at least for a little while.

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