A marketing website to showcase an iPhone app. The purpose is to attract users, educate them about what the app does and how it can help them (marketing), and get them to download the app.
It seems such a set up would be most appropriate:
1-Home Page (showcasing the app, screenshots, text, potentially a video, etc.)
2-Download Page (should be able to enter phone number to receive text with link)
3-User Account Screen (includes images / text / account details -- login from tab bar on top like most modern websites)
a. contains links where they can download files. Marketing people will use this.
4-About page (text / images / links to external sources)