How can call "vrapi_GetPredictedTracking()" function in Unity or accessing vrapi?

Hi.
I'm trying to implement "More accurate HMD Tracking" function on my app.
I have a plan to use HMD Tracking info 200 Hz or more.
In "Mobile Native SDK", I can find "vrapi_GetPredictedTracking()" function.
And I realize this function can be called in other thread.
So I am going to make a "Tracking Thread" and call this function in the thread.
But in Unity I can find any interface of that function.
Anybody can tell me how to achieve "More accurate HMD Tracking" ?

Thank you in advance.