Digital video recorders revolutionized TV viewing for many. Now, they're transforming the role of security cameras. Walgreens is installing DVRs throughout its chain of 6,200 drug stores, using them to aggregate input from the many analog and digital cameras that monitor the sites. Ionit Technologies is providing DVRs with compression technology that decreases file size up to 2,000 times so a single system can be viewed from multiple locations simultaneously. This digitized data can be shared over networks, so views can be sent to corporate or otherwise distributed. That makes it easier to expand the role of security cameras. For example, marketers can analyze traffic flow, which could improve sales.