"Using 468 CCTV cameras, optical sensors and a mobile phone-tracing system, they can tell residents from visitors, Italians from foreigners, where people are co

"Using 468 CCTV cameras, optical sensors and a mobile phone-tracing system, they can tell residents from visitors, Italians from foreigners, where people are coming from, where they are heading and how fast they are moving." Turn off your phone in when in Venice?