Here are a couple of other ideas to elevate this project to the next level:
Replace the dog barking samples with a booming klaxon, a piercing alarm bell, or science fiction self-destruct sound effects. Swap out the fake dog snout attached to the servo arm with a laser pen light that sweeps the entryway. Imagine your front doorway looking like something out of a science fiction thriller!
Add an ultrasonic rangefinder and alter the reaction of sound and motion based on the proximity of the movement being captured. As a intruder comes closer to the sensor, have the volume get louder and the servo move more erratically. The closer one gets to the sensor, the more agitated the Electric Guard Dog becomes.
Upscale your Guard Dog into ...