State-of-the-art head trackers deploy passive (optical) markers and active (optical, acoustic, magnetic) emitters and receivers as well as inertial system components such as gyros, gravimeters and accelerometers. Some advanced systems combine different components, e.g. optical and inertial subsystems, in order to make the tracker more robust against changes in the environment or in the case of occlusions. Generally, these systems are intrusive since they require the user(s) to be tethered to the measurement equipment, or at least to wear some parts of the equipment.

Some approaches need controlled environments. For example, conductive (metallic) materials in the environment may interfere with magnetic trackers. However, these systems may provide highly precise and stable (jitter-free) position and orientation data (6 degrees-of-freedom) over a wide range (up to several metres) with very little latency, and are currently the only available solutions for multiple user tracking. Commercial examples of trackers include the DynaSight sensor (using one passive IR-optical reflector placed on the user's head or up to four active optical targets simultaneously), electromagnetic motion tracking systems are available from Polhemus and Ascension Technology Corporation, inertial motion trackers from InterSense (including special sensor fusion software that combines the input of different sensors) and Logitech's ultrasonic tracker.