The New York City Police Department has come up with a new twist in fighting crime in high-crime areas. The agency now uses what they call "Sky Towers" to watch over a several block area. The sky towers are portable and can be moved from one area to another rapidly. One of the towers has been located at the Redfern Houses in Far Rockaway since a shooting spree in May. Another tower was set up this week at Beach 90 Street and the boardwalk to overlook a problem area on the beach.