In which activity category would you find motion detectors and alarm systems?

Motion detectors and alarm systems are primarily categorized under surveillance and notification because they are designed to monitor an area for security breaches and provide immediate alerts when such breaches occur. These systems serve to continuously observe and detect unusual movements, thereby enhancing security by alerting users or security personnel of any unauthorized access or activities.

Surveillance involves the observation of specific premises or areas, while notification pertains to the system's ability to instantly signal the presence of a potential threat. This places motion detectors and alarm systems firmly in the realm of proactive measures to ensure safety and security, making surveillance and notification the appropriate choice for this question.