Seismic sensor as deer deterrent?

Techlib.com has an intriguing circuit that might be of interest to some back yard deer deterrent experimenters out there.

It detects seismic vibrations from a person or large animal and then sets off a wireless doorbell buzzer for a few seconds to startle whover is nearby.

They label it as a deer repellant for the garden, but I would be concerned about the protective range this thing has. It might work for a garden with low level deer traffic and maybe just one entrance, but our large perimeter here would require dozens of these to cover the whole area. There's no data presented about testing on a real garden, so I would think twice about this approach before investing too much time in it. In fact I feel pretty confident you would get better results with my current design no matter what situation you have, but that's just me.