Warfare technology has come a long way since the days of throwing stones, but that won't keep the military from incorporating rocks into their arsenal of weapons. 

This week at the annual AUSA Army meeting in Washington, D.C., Lockheed Martin showcased developments in their surveillance technology called SPAN (Self-Powered Ad-hoc Network), a "covert, perpetually self-powered wireless sensor network" that can provide "unobtrusive, continuous surveillance" in units so small they can fit in a rock. 

SPAN is a mesh network of self-organizing sensors that, when triggered, can cue a camera or an unmanned aerial vehicle to further study an area, or summon an engineer when a pipeline or bridge structure is in danger or fractured.  It uses proprietary algorithms to reduce false alarms. 

Lockheed touts the "field-and-forget" technology as providing maximum coverage at minimal costs, claiming that the sensors can remain in the field for years at a time without maintenance, powered by solar technology. 

The defense contractor is hoping to sell its spy rocks for surveillance, border protection, pipeline monitoring and bridge security, among other things. 

The SPAN system was originally introduced last year, but this isn't the company's first attempt at making smart rocks. 

Earlier this year, a former Lockheed Martin subcontractor made headlines for attempting to sell on eBay for $10 million an early 2000s prototype of the surveillance rock before Lockheed pulled the plug on the project.  Included in the package were hundreds of pages of detailed development instructions, two years of emails with Lockheed and some hardware — but no rock. 

"Selling this collection of information is an attempt at recouping all or a portion of my investment of time, effort, personal monies, and sweat equity," Gregory Perry told Mother Jones.  The auction ended with no bids. 

And although Lockheed claims that SPAN's inconspicuous sensors "reduce the likelihood of discovery and tampering," it's a safe bet that British intelligence didn't think a rock would be the cause of a diplomatic row. 

Last year, Tony Blair's former chief of staff, Jonathan Powell, admitted that British secret service agency MI6 had planted a spy rock in a Moscow park to communicate with secret agents in 2006 (as depicted below by Taiwanese animators).  Powell said that the "embarrassing" discovery by Russian officials caused a severe diplomatic strain between the two countries, despite the UK's best efforts to laugh off the accusations as absurd Russian propaganda.