On-line processing of data from video sequences is impeded by the need to process the large amount of data acquired by the image sensor Appropriate processing onboard of the sensor can, however, reduce the data transmitted and processed by the tracker. In this paper, we use video sequences from an integrated sensing and processing (ISP) imager to track a variable number of targets; the imager is configured to select and filter data before transmission. The sensor configuration allows selection of (a) pixel blocks to be acquired and (b) filtering operations to be performed on the acquired blocks. We develop a configuration strategy using a particle filter to direct the acquisition and filtering. To track an unknown number of targets, we implement a multi-target tracker using a track-before-detect method. We demonstrate using simulations that the ISP approach reduces the data transmitted to the tracker without loss in tracking performance when compared to traditional sensing systems.