Atomic spin structures assembled by means of scanning tunneling microscopy (STM) provide valuable insight into the understanding of atomic-scale magnetism. Among the major challenges are the detection and subsequent read-out of ultrafast spin dynamics due to a dichotomy in travel speed of these dynamics and the probe tip. Here, we present a device composed of individual Fe atoms that allows for remote detection of spin dynamics. We have characterized the device and used it to detect the presence of spin waves originating from an excitation induced by the STM tip several nanometres away; this may be extended to much longer distances. The device contains a memory element that can be consulted seconds after detection, similar in functionality to e.g. a single photon detector. We performed statistical analysis of the responsiveness to remote spin excitations and corroborated the results using basic calculations of the free evolution of coupled quantum spins.