The Siren Marine yellow wire on all of our devices can be used to monitor an extra bilge area, a motion detector, a pressure matt, a beam sensor, run time on your bilge pump. In this example the yellow wire is connected to an AC relay, that is wired into the boats electrical panel. With this arrangement, if shore power is lost, Pixie or Sprite will automatically send you an alert! Now that's "peace of mind." Learn more at https://sirenmarine.com Pixie - Just $499!