Vandals, drug-dealers and muggers beware: Electronic eyes are watching you. The Parks Department has mounted about 20 cameras across the city in an effort to thwart after-hours crime. The cameras at city parks detect motion and respond with a blinding flash of light and a booming recorded warning. "Your picture has been taken for suspicious activity by the NYPD!" the recording bellows...NYCLU Executive Director Donna Lieberman said her office was investigating Blackburn's complaint. "It sounds bizarre and creepy and we're looking into it," Lieberman said.