In September 2015, the Federal Aviation Administration will open standard US airspace to drones. Not keen on the idea of undetected flying robots overhead, a few engineers and computer scientists have acrowdfunding campaign for a drone detection device called "Droneshield."
Drone Shield is a pager-sized device (remember pagers?), with the incredibly cheap Raspberry Pi computer at its core. It detects drones by sound, using a microphone to pick up the noise before human ears can. It then uses the processing capacity of the computer to understand the signal, screens it against an internal database, before sending an alert out over text message or email.
So far, the project founders already have the database set up, and are hoping that enough interest in the project will eventually allow them to sell the device for about $20. As crodwfunding project rewards, they have a box of parts available for $59 and they'll send out an assembled Drone Shield for $69. So far, the project has raised $232 of it's $3,500 goal, but there's still 46 days left in campaign.
This isn't the first anti-drone concept we've seen. There are clothes, cities, and so-called "active countermeasures", but none of those could fit in a pocket, and even that drone-proof hoody is not terribly discreet. Using Drone Shield while out and about looks to be no more unusual than having a cell phone battery pack.