Seeker's Sight

This sight can be attached to a single two-handed firearm. When this is done, the sight becomes part of the weapon, but can be removed from that weapon with a full-round action. A firearm wielder using a firearm that has this sight can choose to spend a full-round action to either locate an invisible creature within line of sight or make a single shot that ignores the invisibility of a creature that she knows is in the area.