An interface apparatus (20) for tracking by a tracking system (40) of an object(s) in space for position and orientation and for interacting with the tracking system (40). The interface apparatus (30) comprises passive detectable devices (12,14,16,22) trackable for position by the tracking system (40). A mounting device (10,24) receives the passive detectable devices (12,14,16,22) in a known geometry, and is secured to the object(s) such that a position and orientation of the object(s) is calculable by the tracking system (40) as a function of a tracking of the known geometry of the passive detectable devices (12,14,16,22). One of the passive detectable devices (22) is displaceable with respect to the object(s). A displacement of the passive detectable device (22) with respect to the object(s) is detectable to initiate an interaction with the tracking system (40) while maintaining the tracking of the object(s).