Intelligent beams usually require two or more beams to be broken and also the rate at which they are broken can be controlled. For example, your beam may be set to let your dog pass under but occasionally he may leap up and break the bottom beam. If the second beam above is not broken at the same time, no alarm will sound. Also say a bird is to fly through a beam. Birds usually fly at a much faster speed that what someone would walk through, so the beams can be set to ignore a very fast movement through them that is faster than working pace.
Installing the beams so that they are not noticeable is a good idea. On poles, that look like lights in landscaping, means they just blend in with the surroundings and don’t stand out. In some homes with large blocks of land, it is possible to set up 4 pairs of beams( receiver and transmitter) to protect your entire house. This done 10metres or so away from the house, means that they could trigger lights coming on around the property as the first deterant or line of defense against intruders.