Can you build something similar to Twitter? I am looking to build a website where people can post their daily diet into a log via computer or phone application. The website would need a food calorie database so people could track their eating habits easily. It primarily would be a diet and exercise tracker but with some social network features like friends, profile pages, photos, ability to display diet to public or keep private etc.. The diet tracker could produce statistics for users such as calories consumed, fat, protein, carbohydrates, etc.
As far as design is concerned I would want something fairly simple. The key would be ease of use for people wanting to track their calorie intake.