A trigger activated switch for a firearm is disclosed. The switch comprises a Hall-effect sensor configured to be mounted in the housing or frame of the firearm, and a magnet disposed on a retractable member coupled to the trigger of the gun. The trigger comprises a firing module rotatably coupled to the housing to have a range of motion with respect to the housing from a non-firing position to a firing position. The retractable member is moveably coupled to the firing module and articulates between a non-engaged position and engaged position with respect to the firing module. The Hall-effect sensor is attached to the firearm housing in proximity to the magnet when the retractable member is in the non-engaged position. Motion of the retractable member from the non-engaged position to the engaged position causes the magnet to articulate away from the sensor, which then activates an auxiliary device upon sensing motion of the retractable member.