A method for surveillance of a point on a target. A portable device is obtained, which includes: a laser range finder operable for measuring distances between the laser range finder and a target, an alarm operable for generating a perceptible signal, and a microcontroller. The microcontroller is configured and arranged to receive an initial distance value and subsequent distance measurements from the laser range finder and compare the values wherein an alarm is triggered id the change in the values is within a specified range. Subsequent steps include statically positioning and operating the device to measure the distance to an object comprising a moveable obstruction to an ingress or egress and monitoring the generation of any signal by the device indicative of movement of the object to permit ingress or egress.