Besides opening up the camera application and activating the shutter, voice command could also allow users to keep or delete a particular snapshot. The patent application was filed by Microsoft back in 2011, although the USPTO is just bringing it to our attention.
Part of the application includes a training period to let the technology "learn" your voice and the mannerisms of how you speak for improved accuracy. In addition, users could replace a default phrase with another command. For example, "take picture" could be changed to any rarely used phrase to prevent the taking of an accidental picture. Besides a human voice, a particular noise like clapping hands can be set to fire the camera. We wouldn't recommend that setting for those with the Clapper (Clap on, clap off).
source: PatentBolt via WPCentral