No, it's not the flat, bottom-dwelling sea creature you take efforts to avoid when you're wading along in the ocean. This breed of StingRay is an elaborate surveillance system that simulates a cell phone tower and is used to locate and track individual cell phones. 

Unites States authorities have been using these sophisticated surveillance systems to track criminals for at least five years now, but now privacy activists are raising some serious concerns. Today, the ACLU will urge a federal court in Arizona to disregard evidence obtained via stingray surveillance, in what could have important implications for use of the method without a warrant. 

The issue is also being raised in California after the ACLU obtained "troubling" emails through a Freedom of Information Act request, which showed that Department of Justice officials in northern California acknowledged not being forthright about the use of StingRays. 

The Electronic Frontier Foundation even referred to the technology as the, "biggest technological threat to cellphone privacy that you don't know about."

Washington Post reporter Ellen Nakashima, who's written about this topic, joins the show with more.