The invention relates to a surveillance device for installation in a domestic property, comprising event execution means and processing means for generation of commands for at least one event reaction body, characterised in comprising a network ( 6 ) of cooperating non-hierarchical modules ( 1, 2, 3, 4 ), each comprising detection data processing means ( 8 ) and internal communication means ( 9 ), configured for exchange of surveillance data between modules. The invention further relates to a surveillance installation comprising several such devices.