AeroScope uses the existing communications link between a drone and its remote controller to broadcast identification information such as a registration or serial number, as well as basic telemetry, including location, altitude, speed and direction. Police, security agencies, aviation authorities and other authorized parties can use an AeroScope receiver to monitor, analyze and act on that information.

http://www.dji.com/newsroom/news/dji-unveils-technology-to-identify-and-track-airborne-drones

Good work DJI! Let's hope the evil criminals and terrorist don't have the ability to modify the registration and serial numbers, or this will just be like the war on guns, where criminals and law enforcement are the only ones that have access to such force.

Hope this will give 'us' a bit less reason to add more regulations.

Sounds a lot like ADS-B, a project I helped develop over 20 years ago for UPS Technologies.  I have my doubts since this is A) low altitude B) too much clutter.