A system for marking a route, path or boundary. The system may comprise a plurality of modules, each of which comprises a signaling device, a radiofrequency apparatus and control circuitry. Such modules are positionable in an array which marks the route, path or boundary. When positioned in the array, the modules undergo radiofrequency communication with one another and the control circuitry causes the signaling devices of the modules to emit warning signals in sequence from a first-positioned module of the array to a last-positioned module of the array.