UK based The Pixel Farm have been been designing software for over 8 years, you might have come across their tracking products PFTrack or PFMatchit  So this iPhone App is a bit of an adventure out of the world of high end VFX and compositing and into the consumer "There's an App for that" market.

The app lets you control colour grading on a Mac via one virtual trackball on an iPhone. The downside is that you have to download a standalone app that does the colour correcting so you can't have this thing controlling a plugin in FCP or After Effects.

You can however save your corrections in ASC format and use them elsewhere. Here's the link to the iTunes download page. For the host app you will have to visit the AirGrade webpage as they require a login