A live human being visible across the property, with the ability to react dynamically to any situation provides a deterrence factor that is unparalleled. However, the effectiveness of that human can be greatly increased when augmented with technology. Probably the most common example is the use of cameras to allow the security officer to secure more areas than he is physically in, and add deterrence by showing an area is always under surveillance.
Cameras are one of the oldest tools in security, but relatively recent improvements are making them easier, cheaper, and more effective than ever. Even the cameras contained in most cellphones today have vastly superior resolution and night vision capabilities than was possible just a few years ago. Standalone security cameras take these improvements even further, with new technology such as facial recognition, digital storage, and movement tracking systems becoming mainstream.
The value of these systems is not debatable. In Detroit, many businesses have adopted highly visible cameras, with a bright green light leaving no doubt that the cameras are recording. The drop in crimes such as carjackings, and even homicides in the affected areas has been so pronounced that soon all business open late at night will be required to have the cameras installed. The games in Korea are making use of over a thousand cameras that even have X-Rays built in, in order to search cars and bags for hidden persons or firearms. While the innovations make for a more secure environment, the basic principle that a person will be reluctant to commit a crime when he knows he is being watched has been true since the first crimes were committed.