Cookbook with 2D Barcode and app

How often do you look at a recipe in a cookbook and it makes enough for 4 people? When you only need to feed 2? Or 10? If I scale it, what do I need to do with the baking temperature and time? How do I do 2.5 eggs? You know, stuff which isn't blatantly obvious.

The barcode has quantities and scaling information which might confuse the average person. You can it with an app on your smartphone/tablet and tell it how many people you want to feed. It tells you how to scale it up/down, including baking time, temperature, etc.

You're on a gluten-free diet? Low carb? Need to do some substitutions? Again, that can get complicated. Better to let an app do that. That app will need data, preferably WITHOUT needing to hit some external website. You can put quite a bit of data into modern, 2D barcode, especially if the data is compressed.

Edit: turning 3D barcode into 2D barcode. Dunno what I was thinking. A 2D barcode should be sufficient, as you can stuff a fair number of bytes into a square inch.