Avani, I love how you are preserving cultural traditions in your approach. I wonder how the role of beliefs will play in the substitutions part of your app - what guidelines will you use for what's considered a "healthy" substitute? Have you considered guiding principles or motto (e.g., Michael Pollan's "Eat real food. Not too much. Mostly plants.") to ensure that everyone in the virtual community is on the same page? We've experienced negative consequences in the past where nutritional guidelines were incomplete or downright incorrect, which has led to the creation of Frankenfoods where the fat is stripped out and replaced with sugar and other additives. Nutrition science is still very new, and I'd hate to see natural ingredients used in traditional cooking replaced by the latest fad (like applesauce instead of olive oil - why?!).
In addition to the ingredients themselves, have you considered encouraging traditions around food like everyone in the family sitting down and eating a meal together, or growing/shopping for foods together? I find it fascinating how different cultures have so many beliefs around the process of preparing and eating meals, and would love to learn about these different behaviors. For example, Europeans eat salad at the end of the meal to cleanse the palate. Sharing and preserving these traditions make the experience of eating more mindful and can remind us that taking the time to appreciate food and health is important. If you haven't seen Jiro Dreams of Sushi, you should check it out - I highly recommend!
You may want to check out Doug Rauch's new grocery store that sells produce that would normally go to waste in an affordable grocery store: http://dailytable.org/about-us/our-story/
The logistics seem to be the major challenge here. Where will the food come from, how/when does it get to the cook? How do you ensure the cook has enough for all interested people? How does this work for families with 6, 10 or more people? I think for many families, eating a dinner together as a family is important, but how will everyone fit?
Have you considered a potluck model, where everyone brings a dish? Is there a role for "buying in bulk" to reduce meal costs?
As someone who struggles with cravings for sweet things, I'd love this app! I have a background in health and I know that carrots are better for me than doughnuts (hopefully most people know this), but I still find it hard to simply make the healthier choice.
A major issue with cravings is that a lot of time it isn't a matter of hunger, but that the person is feeling bored, tired, stressed, lonely, etc. In your example, I love that you give Bob ideas for alternatives to the doughnuts, but for many people, they reach for the doughnut because it's cheap, tasty, and easy. Even if the person reaches for the healthy snack, it still doesn't address the underlying issue: using food to satisfy the stress, loneliness, or other emotion they are using food to help soothe.
I'd love to see some emotional support in your app, similar to how a person in AA has a sponsor they can call whenever they are experiencing cravings, whenever a person starts craving a snack, other members of the community can instantly help them work through it and give them ideas for non-food alternatives to address what they need at that time - a walk, some meditation, or even just offering words of encouragement can go a long way.
What I love about your idea is that you can easily test a very low fidelity prototype just using text messaging, for example. You can set up a group text where over the course of a week or so, people in the group agree to text "I'm craving X!" whenever they have a craving, and the other members in the group can provide suggestions. Make sure the team logs their failures/successes to learn best practice for what works and what leaves room for improvement.