This company LDP LLC sells converted IR and UV cameras that are being used by Conservation Drones. What really piqued my interest is that they claim to do UV, IR, and visible light in one camera, and sell one-camera NDVI rigs. How? I can't quite tell-- they remove and replace the filters with custom ones, and then I think, based on their conversions page, that it has something to do with the white balance settings.
They're doing NDVI post-processing in ImageJ, a java library for image processing.