I consider myself pretty clued-in technically, but this never even occurred to me! Presumably this is possible with European phones too?

News.com: The FBI appears to have begun using a novel form of electronic surveillance in criminal investigations: remotely activating a mobile phone’s microphone and using it to eavesdrop on nearby conversations.

The technique is called a “roving bug,” and was approved by top U.S. Department of Justice officials for use against members of a New York organized crime family who were wary of conventional surveillance techniques such as tailing a suspect or wiretapping him.