This fuel pump safety switch is designed to shut off your electric fuel pump when the engine oil pressure drops below 15 lbs.  It can easily be "Tee'd" into the oil pressure ending unit off the block.  Designed for 12 volt systems.  A second version is also available in a single pole version.  This unit uses a normally open circuit preset to 6 PSI.  This unit is commonly used as an ignition kill in the event fuel pressure were to become dangerously low.