We started developing a stereo camera set-up so that we could capture two images simultaeously -- one visible, one infrared. The visible imagery can be stitched normally, or overlaid with the infrared to create NDVI - Normalized Difference Vegetation Index.
NDVI can be used to identify not only the presence of but also the health of vegetation. Since the 1980's NDVI has become one of the important tools for mapping and monitoring vegetation.
Only two bands are required: Red channel 0.62 – 0.67 μm, and Near IR channel 0.84–0.87 μm. On the MODIS satellite these are Bands 1 and 2 respectively.
Another use of a stereo camera rig would be for stereoscopy -- a technique which uses two slightly offset images (from two cameras as far apart as human eyes, for instance) to recreate the illusion of depth in a digital image.