Cool. It's for eating disorder recovery. Mostly diary style. List 3 gratitude a day, gives a daily affirmation, a food diary set up for the exchange system most ED treatments use, an exercise diary, a place to make an action plan when people have urges to use behaviors. A list of resources.
It could actually be an ebook, except there needs to be a place for people to write in it. Huh. Is there an ebook form for diaries?
I was amazed there are almost no apps out there for eating disorder behavior management. I've found about 3. So you have thousands and thousands of people - a lot of them teens and early 20's, a lot of them with money (affluent parents) who are writing this info down on paper everyday to take to their nutritionist. And a lot of the non-specific apps for food journals are overtly pro-weight loss which is toxic for people with ED.
That's actually a good idea and very eat to get started in. Find a weight loss diary app you like and use that as the backbone. Strip out all the weight-loss stuff and add back the ED recovery stuff. You have a target market and semi-relevant model to follow to avoid a lot of the 'unknown' costs. Plus your market is one that is accepting of technology so an app would work.
Coming to a developer with a set-up like that will actually get you a decent estimate on a price. I want the backbone of "Weight-loss Diary" with these changes. We are going to replace "current weight" with "consecutive days of... ". Also I need it to do "x, y and z" for these reasons.
One other person/market I'd talk to is an ED doctor about the sort of things that they have seen that have been helpful in speeding patient recover and seeing if you can add those in. I don't know anyone with an ED (my family is strictly on the needing the weight-loss side) so I'm not even sure what sort of things would be helpful there.
Last point - try to plan phases if your ideas get too out of hand. Phase 1 can be the diary with a weekly emailed summary to a doctor/parent/SO. Phase 2 is a message board/community. Phase 3 is adding in recipes and other extras. This will let you control costs and get something to market to build around (and fund later updates).
-side note/idea - maybe go after the doctors with an app that they can give to their patients for free to help keep them on track. Bulk pricing (every 10 memberships are $xx/month). They might be able to write it off as a business expense (lower actual cost for them than you would charge), and you would get someone that helps to push your product from a position of authority. Of course this would start with 10 free memberships (or 3 months of memberships) to show the doctor the benefits of the app.
I like the idea, best of luck.