Apparently, there is an API by AisleFinder, called Supermarket API. Supposedly they cover large chain stores and return product aisle location as part of the response. However, lots of people complain that this info is almost always old/wrong, so it's pretty much useless. They have their own iPhone and Android apps (I'm assuming built around that API). On top of that, it's not free. Well, I was kinda expecting that.