"It used to be that security systems could protect only what was right in front of them," said Geoffrey Fowler at The Wall Street Journal. But Aura, a $500 home security system, can "see" through walls and around corners so you don't have to fill your house with cameras or place motion sensors near every door.

The device spots intruders through disruptions in the invisible radio waves that make up your home's Wi-Fi network. "These are like ripples in a pond, flowing through walls and bouncing around in pretty regular patterns, until something — or someone — gets in the way."

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Aura's software is smart enough to differentiate normal disruptions — like a spinning fan or family pet — from potential threats, but it can still be tripped up by a home's layout or an especially active Fido. Also, unlike security cameras, "it won't produce photographic evidence for the cops."