Stacked image sensor systems combine an image sensor, memory, and processors using 3D technology. Stacking camera components that have traditionally been packaged separately provides several benefits: very high bandwidth out of the image sensor, allowing for higher frame rates; very low latency, providing opportunities for image processing and computer vision algorithms which can adapt at very high rates; and lower power consumption. This paper will review the characteristics of stacked image sensor systems and discuss novel algorithmic and systems concepts that are made possible by these stacked sensors.