From what I can tell, it needs to be an actual app that delivers your content - ebooks as apps are one of the biggest categories at the App Store.
There are lots of companies that will package your content feeds and create the app in your name - That's what I did with one app for 47hats, the Startup Success Podcast and the Twitter feed from my startup. I went through Appmakr.com. iTunes link You can do a free, no ad app, an ad-supported app (splitting revenue) or a for sale app (but you need to be in the Apple iPhone Developer program for that - $100).
Also, read this post by Seth Godin, try out the app of one of his older books (search for Vook) and you'll see the potential this has.