The product should already have a UPC code that is trivial to capture. From there, it would be a simple matter of looking up that code to map it to its nutrition information. There may even be databases (eg: FDA) where this is available. MyFitnessPal seems to have the nutritional info on just about every product I've scanned, and I can't tell if they crowdsourced all that data input and/or if they seeded it with some database.