This just may be the fanciest, most tricked-out cookbook in all of iOS-dom. The $80
Modernist Cuisine at Home app for iPhone and iPad is a multimedia updating of the classic cookbook, with hundreds of recipes, photographs, and videos, plus tools for scaling recipes and making shopping lists that can sync between your various devices. There are more than 400 recipes in the app, sporting more than 1600 photographs. It’s a visual feast, all by itself.