We present an embedded software application for the real-time estimation of building occupancy using a network of video cameras. We analyze a series of alternative decompositions of the main application tasks and profile each of them by running the corresponding embedded software on three different processors. Based on the profiling measures, we build various alternative embedded platforms by combining different embedded processors, memory modules and network interfaces. In particular, we consider the choice of two possible network technologies: ARCnet and Ethernet. After deriving an analytical model of the network costs, we use it to complete an exploration of the design space as we scale the number of video cameras in an hypothetical building. We compare our results with those obtained for two real buildings of different characteristics. We conclude discussing the results of our case study in the broader context of other camera-network applications.