Wikileaks has posted the manual for BBN Technologies' Boomerang II sniper-locating system. The device consists of a three-dimensional seven-microphone array connected to a DSP that is mounted on a HMMWV (Humvee). Upon detection of a gunshot, the system calculates the direction of the shooter and presents this information to the HMMWV crew using audible and visual indicators.
[from Reddit]