The interest in low-cost and small size video surveillance systems able to collaborate in a network has been increasing over the last years. Thanks to the progress in low-power design, research has greatly reduced the size and the power consumption of such distributed embedded systems providing flexibility, quick deployment and allowing the implementation of effective vision algorithms performing image processing directly on the embedded node. In this paper we present a multi-modal video sensor node designed for low-power and low-cost video surveillance able to detect changes in the environment. The system is equipped with a CMOS video camera and a Pyroelectric InfraRed (PIR) sensor exploited to reduce remarkably the power consumption of the system in absence of events. The on-board microprocessor implements an NCC-based change detection algorithm. We analyze different configurations and characterize the system in terms of runtime execution and power consumption.