What was the phrase in the Apple developer guidelines?
"Certain kinds of apps, such as dating, flashlight, sound effects, wallpaper, simple timers, and fortune telling, are well established on the App Store and we will not accept new submissions unless they offer a meaningfully different or improved experience"
Arguably, this isn't a meaningfully different or improved experience (it's the same boring thing as every other photo-as-calorie-counter-that-never-works-right, unless you count them adding monetization through a 'premium' subscription as a meaningfully different experience), so Apple should have just tossed it from the platform.
you're right that it's never accurate. neither are we though - people under-report their own intake by 20–40% in actual studies. the photo just has to beat "didn't log anything", and it does.
