A system for making sure that two wireless devices (a perimeter-anchoring device and a constrained device) are not separated too far apart by having a dynamic perimeter that follows the perimeter-anchoring device as it moves. In some embodiments, the size and/or shape of the perimeter is controlled by machine logic based rules, based at least in part, upon a set of environmental factor(s). Some possible environmental factors include: line of sight, pollution, noise level, presence of stranger(s), streets, traffic, body(ies) of water, contamination, allergen, or blocking obstruction(s).

A system for making sure that two wireless devices (a perimeter-anchoring device and a constrained device) are not separated too far apart by having a dynamic perimeter that follows the perimeter-anchoring device as it moves. In some embodiments, the size and/or shape of the perimeter is controlled by machine logic based rules, based at least in part, upon a set of environmental factor(s). Some possible environmental factors include: line of sight, pollution, noise level, presence of stranger(s), streets, traffic, body(ies) of water, contamination, allergen, or blocking obstruction(s).

The invention relates to a security system designed to recognise, by means of the presence and/or content of a status enquiry signal of at least one security unit, whether or not at least one security unit is located inside the security zone. The security system includes an alarm generating unit which is designed to generate an alarm signal if it has been recognised that the at least one security unit is located outside the security zone. The invention further relates to a method for emitting an alarm signal, a bus with a security system and a use of a security system.