Perimetr

Wired magazine run an extremely interesting article about the Russian doomsday device called Perimeter (or Perimetr). It's a system that's designed to launch a nuclear strike back at the enemy even if there's no one left to actually start the missiles. Autonomous ground sensors would record the devastating blow of a nuclear attack and retaliate automatically.

Wired.com: Inside the Apocalyptic Soviet Doomsday Machine

UPDATE: I found another, similar article in Slate from 2007 which goes even more in-depth about the system, called Perimetr here. Even more interesting are the references to Dr Bruce Blair's Nuclear Recollections, more of which I will be posting soon.

Did the Soviets really build a "doomsday machine"? - By Ron Rosenbaum - Slate Magazine