Cookbook and recipe apps aren't exactly new to iOS. However, Recipe Kitchen doesn't aim to be just any old recipe app.
Many of the expected features are present in Recipe Kitchen; such as a sizable selection of food items to make, recipe sharing, and cooking timers. However, it can also keep track of all the ingredients you have in your kitchen. You can scan barcodes to add new items, create shopping lists for what you're running low on and sync it to multiple devices (so that other family members will know what to pick up while they're out), and even call up a list of recipes that are available based on what ingredients you currently have available.
Sounds super-handy, no?