Which device helps security personnel monitor an environment?

Surveillance cameras are specifically designed to assist security personnel in monitoring an environment. They provide a visual feed of the area they are observing, allowing security staff to keep an eye on activities in real time or review recorded footage later. This capability is crucial for identifying suspicious behavior, deterring crime, and documenting incidents for future reference.

While walkie-talkies are useful for communication among security personnel, they do not provide visual monitoring of the environment. Cellphones can facilitate communication and may have camera functionality, but their primary use is not dedicated to monitoring. Computers can be used to analyze and store footage from surveillance systems, but they do not directly monitor the environment on their own. Therefore, surveillance cameras are the optimal tool listed for ongoing observation and security awareness in a given area.