Pika is a full-featured app.net client for iPhone with a unique approach to interface.
Pika's top design goal is to minimize navigation and "chrome" -- while you're browsing, all you see is posts. Scroll up a bit and the navigation pops back into view.
Includes features like:
- Push notifications for mentions, reposts, follows and stars
- Stream marker syncing
- Photo uploads via CloudApp
- Location posting
- View attached images and locations
- ...and much more