Even if you're not into HDR photography, this is one to check out. High Dynamic Range photography creates an image from multiple exposures that are combined to overcome the limitations of automatic exposure control in cameras. The technique can recover details that would be lost in shadows, and keep bright areas, like the sky from blowing out.
The update to Pro HDR, which has just been released, has a new fully automatic mode. Instead of taking two pictures with your iPhone, and manually pointing to the brightest and darkest areas, this new option analyzes the scene, sets the exposure accordingly, and then takes the two images without any user intervention. You can also use the manual mode if you prefer. The app also claims faster image capture and better alignment.