Android: There are plenty of camera apps that help with exposure, special effects and editing. Camera51 is the first we've seen that helps you find the best angle for a well-crafted shot.
Camera51 is very simple to use: just touch the focal point, and the app will tell you what direction to move your camera. When you snap the picture, it's automatically saved to your gallery, where you can edit it as you please. The developer video below shows how it works:
The app is available for free in the Google Play Store. It also supports grid lines, flash and video. The positioning feature isn't available for video, however.