  Many sensor networks, including large particle detector arrays measuring
high-energy cosmic-ray air showers, traditionally rely on centralised trigger
algorithms to find spatial and temporal coincidences of individual nodes. Such
schemes suffer from scalability problems, especially if the nodes communicate
wirelessly or have bandwidth limitations. However, nodes which instead
communicate with each other can, in principle, use a distributed algorithm to
find coincident events themselves without communication with a central node. We
present such an algorithm and consider various design tradeoffs involved, in
the context of a potential trigger for the Auger Engineering Radio Array
(AERA).
