LAPD Spied on 21 Using StingRay Anti-Terrorism Tool (laweekly.com)
The LAPD used highly controversial counterterrorism technology called StingRay 21 times in run-of-the-mill criminal investigations over just a 4 month period. StingRay mimics cell phone towers so cell phones in its range will reveal their real time geolocational data. StingRay raises serious privacy concerns because it does not distinguish between cell phones targeted in an investigation, and those owned by innocent individuals within range of the technology, sweeping up the real time location data of innocent people.
See the ACLU blog on StingRay technology: http://www.aclu.org/blog/national-security-technology-and-liberty/court-uncovering-stingrays-troubling-new-location