We analyze an agent-based distributed algorithm with exponentially distributed waiting times in which two types of agents interact locally over a geometric graph, and based on this interaction and on the value of a common intolerance threshold $tau$, decide whether to change their types. This model is equivalent to an Asynchronous Cellular Automaton (ACA) with extended Moore neighborhoods, a zero-temperature Ising model with Glauber dynamics, or a Schelling model of self-organized segregation in an open system, and has applications in the analysis of social and biological networks, and spin systems.