I am working on something like this. www.dietmanager.com. I also tied it in w/ the usda food database web service to break things down even further and tied in a feedback loop so that people know what ingredients trigger their conditions etc...
To get this info local chefs can upload their menu's. Their food items are run against the USDA food database then categorized against which dits allow those things and which do not. I currently have support for 455 diets
2. Restaurants
Some of this menu info from the restaurants uploading their menu's and some comes from info that I can get from online sources; as with the local chef menu's I use the USDA food database here to know what meals qualify for what diets
3. Recipes
This one I have not quite figured out yet.
My app does not work like others in that it does not recommend "Places" it instead allows you to search for what food you want and it finds meals based on that food item that also match your dietary preferences (which may or may not be a pre-defined diet)
