Worried about drones spying on you? Soon, a device might be able to send you text and email alerts that let you know when a drone is nearby.

 A Washington, D.C.-based engineer is working on the "Drone Shield," a small, Wi-Fi-connected device that uses a microphone to detect a drone's "acoustic signatures" (sound frequency and spectrum) when it's within range.

The device will cost $69 and will be about the size of a USB thumb drive. It will use Raspberry Pi – a tiny, $25 computer – and commercially available microphones to detect drones. He says he imagines that people will attach the Drone Shield to their fences or roofs to protect their home from surveillance.