Door Bells was previously a RookSoft application, but then the undead at Pink Zombie Studios got ahold of it and zombified it… And the zombies made DoorBells free! DoorBells is now a free download through the Apple iTunes Store. DoorBells is a new door bell for the electronic age for those people who arrive outside somebody’s house can calls them on the mobile to let them know that they’re outside. DoorBells allows you to set up as many people as…