A proximity alert functions by detecting and producing an alert in the presence of nearby objects and people without having to make physical contact with them. A proximity sensor is used to do this. Proximity alerting works by emitting an electromagnetic field or infrared radiation and detecting any changes in the field; when a change is detected an alerts is issued.

Proximity sensors typically have high reliability and a long life because they do not rely on mechanical parts and do not require physical contact with the sensed object. Proximity sensors are also available on mobile phones – when a person is within specified range the device’s lock screen interface is displayed and the phone emerges from sleep mode. Proximity sensors can also be used to recognize hand gestures and can replace vision or depth camera solutions for detecting hand gestures.