Serge Ramelli has Lightroom 4 Retouching (iTunes Link) for the iPhone, iPod Touch, and iPad in the iTunes App Store for FREE (regularly $5.99) for a limited time.

Serge Ramelli a french photographer who specialized in urban/landscapes photography over the last 6 years and is known for his very simple way of teaching. 
You will find various unique tips and tricks to get the most out of your photos. NO technical jargon used without a simple explanation. More importantly get straight to work doing stunning landscapes.

 Included with the app is access to amazing high-res pictures (raw files), so you can follow along the retouch process and get the same results.