[Joe Iley Sanders]

I just had an "invisible fence" installed around the perimeter of my yard. Essentially it's an underground radio antenna that triggers a tone and then a shock if my pet approaches it. It is intended to keep the pet from leaving the property.

This could be augmented with relatively cheap seismic dectectors which could sound an alam indoors if something crossed the perimeter. The "antenna" wire could be used as a conduit for the electrical signals from the seismic dectectors (which require no power). Or multiple channels could be deployed to actually pin-point the intrusion spot. Either option could be very economically installed together with the pet system.

Reward: Testing and installation on my property. Expanding the current 1 acre primeter to my entire 5 acres.