Find out when headset started actively tracking (in Unity)?

Hi! Is there an event or bool to check for when the headset becomes active & actively tracking? Basically, when the OVRCameraRig -> TrackingSpace -> CenterEyeAnchor position becomes non-Vector3.zero (which is what I'm currently checking for and which works, but seems hacky)? I'm needing this to position one on a seat in relation to the scene, based on one's in-rig location. Thanks!