How do I make a selection using Raycast with a VR headset?

I have a HTV VIVE VR headset. I currently am working on a VR environment in Unity, in which the player needs to make a selection. I want the selection to be made by using the headset, essentially the player would gaze at a box for x amount of time, and the selection would be made. I do not want to use the controllers to be used just the headset.