PROTECH VIDEOWAVE has several alternatives including installing a fence-mounted intrusion detection system (on the existing fence/wall) to detect cutting, climbing on or lifting the fence or cutting through the wall. Once a breach occurs, an alarm is sent to your control center which can verify activity by slewing a camera to the intrusion location. While fences by themselves can deter intruders, adding intrusion detection technology on the fence to tell you what is happening enhances the solution. Essentially you are turning a dumb fence into a smart one.
Another option is adding a secondary layer of security, with infrared beams or microwave barriers that form an invisible fence. This is also a great solution on sites that do not have an existing fence.