alphadogg writes with a distressing bit of analysis of the training materials acquired by the ACLU
last week. From the article: "Many law enforcement agencies across the U.S. track mobile phones as part of investigations, but only a minority ask for court-ordered warrants, according to a report released Monday by the American Civil Liberties Union. More than 90 law enforcement agencies said they track mobile phones during investigations, but only six reported receiving court-approved warrants after demonstrating that there's probable cause of a crime, according to an ACLU report based on public information requests filed by the group last year."
The ACLU has a handy page allowing you to see if your local PD engages in such practices