I am building an Android application based on Augmented Reality. The main idea is when user opens up my application, by default device\'s camera starts in preview mode. Based on
you can check the code of mixare, an augmented reality browser released under the GPLv3. The repository is available at: http://github.com/mixare/mixare
There are a lot of details you have to take care of, starting from the fact that the Field of View of the camera is only programatically available since version 2.3 (IIRC) of android. You find these and lots of others in the compatibility class.
HTH, Daniele - mixare team