Visual monitoring with CMOS image sensors opens up a variety of new applications for wireless sensor nodes, ranging from military surveillance to in vivo molecular imaging. In particular, the ability to detect motion can enable more intelligent power management through on-demand duty cycling and reduced data-retention requirements. Conventional imager designs focus on achieving higher resolution, frame rate [1], or dynamic range [2], resulting in power consumption levels that are unsuitable for battery-powered wireless sensor nodes [3].