Within this month, about half of St. Louis County police officers in US will be recording every call for service using tiny video cameras on their chests, glasses or collars. Several companies are lending free technology to police departments in hope of landing lucrative contracts in an industry that surged after a national outcry about the Ferguson police shooting. In St. Louis County, 188 police officers will be using cameras in the north and central county precincts, as well as in Jennings and Dellwood.