PHILADELPHIA (AP) -- Police in Philadelphia have started testing body cameras, a move that comes as the head of the force joined a presidential task force on modern law enforcement. The department says up to 31 officers began wearing body cameras Monday to record interactions with civilians. It's a pilot program that involves testing several brands of the small, lapel-mounted devices over six months. The announcement came as President Barack Obama tapped city police Commissioner Charles Ramsey to lead a Task Force on 21st Century Policing. Obama on Monday also proposed a community policing initiative that would include $75 million to help departments across the U.S. buy about 50,000 body cameras. Demands for police to wear the cameras have increased since an officer in Ferguson, Missouri, fatally shot teenager Michael Brown in August.