It begins with cameras, but doesn't end there. With IP/digital based systems now coming online you can do so much more with technology. Video analytics is becoming more accurate and useful along with other technologies. The challenge is affording the cost of these systems and staying abreast of the technology churn that can soon make your system out of date and worst of all "not supported."
There is no turning back at this point. Remote sensors, radar, sonar, automatic pop-up barriers are all on the menu for you to select from. This combined with modern access control systems will allow organizations to know who is in a building, when they arrived and departed.
With all technology there is a human element. One is getting the executive level support to fund security, having staff follow security protocols and then finding the technologically talented people to operate and maintain the systems.
I'm sure there will always be some gates, guards and guns in the mix--but there will be a computer and technology added to what makes up a modern security system.