http://www.physorg.com/news4211.html

The Air Force Air Armament Center should still have an office that provides seismic intrusion detection devices for Air Base Defense. During the Vietnam war, seismic and acoustic devices were air dropped to precisely measured points such that enemy infiltration from North Vietnam could be detected, tracked, and subjected to air attack. A few years back there was great emphasis on Dual Use technology, the objective being to find civilian applications for military technology. I suspect there still is, and your research might be able to benefit. You might want to try and contact Dr. Steve Butler, Director of Engineering and Technical Management, Headquarters Air Force Materiel Command, Wright-Patterson AFB, Ohio

Elephants do wander around in packs, composed of family groups so I suppose it is no surprise that they have an elborate communication system. They rarely show signs of great intelligence. Unfortunately this is when they are rogue and so not approachable.