Clicks resembling those produced by odontocetes (toothed whales, dolphins and porpoises) arise from various sources, but not in the semi-regular sequences called ‘trains’ that are specific to the echolocation of these animals. The T-POD and C-POD (both developed by Chelonia) are the only commercially available systems that implement train detection for odontocetes. The output has been experimentally validated against visual and acoustic observations in many environments to monitor a diverse range of species, including deep diving beaked whales. These static autonomous click detectors are relatively low-cost systems, for which we have a proven track record for pioneering work with excellent results. Researchers typically deploy numerous PODs and accept the often high probability of losing some units or worse, but, to date, our own custom-designed deployment and mooring configurations have secured a 100% recovery rate.