MacPhun, the makers of FX Photo Studio, are working on a selective-coloring photography for iPhone called Color Splash Studio. Unlike similar apps already available in the App Store, FX Photo Studio comes with a slew of tools that allows you to further customize your photos including contrast, brightness, saturation, and hue. You can focus these edits to just the background or just the colored portion of your photo. You can also apply various filters (like sepia) to your background, making it more interesting than the traditional black and white backgrounds.
FX Photo Studio is already available in the Mac App Store [$2.99 - Mac App Store link] and will be available on the iPhone in mid-February.
We got a sneak peak of Color Splash Studio for iPhone while at Macworld 2012.