Forget asking Siri(Opens in a new window) for the weather. A new microscopic temperature sensor can live in the walls or behind a layer of paint and recharge using radio waves.

The wireless gadget, from researchers at the Eindhoven University of Technology in the Netherlands, measures only 2 square millimeters and weighs just 1.6 milligrams. Despite its small size, though, the sensor “has a specially developed router, with an antenna that sends radio waves to the sensors to power them,” the university says.

At this point, its range is just under an inch, but that’s expected to expand to about 3 feet within the next year and, ultimately, 16 feet.

Why would you want this device to sense temperature? As the researchers explained, “the smart buildings of the future will be full of sensors that will respond to the residents’ every need, and will be as sustainable as possible. Like heating and lighting that only switches on when someone is in the room.”

Once the device reaches its energy capacity, the sensor switches on, measures the temperature, and sends a distinctive frequency to the router. The router can then deduce the temperature based on that signal.

According to the university, the same technology can be implemented in other wireless sensors, to measure movement, light, and humidity.

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“The application areas are enormous,” Peter Baltus, Eindhoven University professor of wireless technology, said in a statement(Opens in a new window), pointing to payment systems, wireless identification, and industrial production systems.

Best of all, the sensors’ price will be about as tiny as it is: mass production should keep costs down to 20 cents per unit.