If you've played enough DayZ, you've had plenty of time where it's nothing but you and the zombies. That's going to be changing soon as the Bohemia Interactive team that's handling DayZ showed off the newest addition to the game, dogs.
In the video below, you can see that your dog can be given commands that's going to help you survive the apocalypse. The "track" command will have the dog go find animals that you can hunt for food, and the "warn" command will have the dog alert you when hostiles are nearby.
No dates have been set on when the dogs will show up or if sad music will play if the dog dies.