the Waterproof Mini Camera (infrared-ready)
Be aware that this camera must be opened and modified before it can capture near infrared light. The product description at the Public Lab Store is quite easy to misinterpret. I could find no information about converting this particular model, and regardless, the product description says that the model may vary.
Will this be suitable for indoor hydroponics farms?
The standard interpretation of NDVI values assumes that the photos were taken with the plant foliage illuminated by sunlight. If your plants are illuminated with artificial lights or sunlight filtered through modern windows, the ratio of NIR to visible light could differ enough to make NDVI meaningless.
Also how do I get the NDVI numerical values?
The Photo Monitoring Plugin for Fiji will produce a grayscale image (single channel) with the NDVI values for each pixel encoded in each pixel. Fiji allows manipulating these values, e.g., the mean value within a polygon can be displayed interactively. Fiji allows scripting.