HTC has since the launch of the Vive Pro been keeping quiet about what the dual camera setup on the front can be used for. Now they have unveiled that the cameras can be used to enable rich AR experiences that also can seamlessly mix AR and VR.
For developers, this means that the cameras gives access to more than just raw images, but via the VIVE SRWorks SDK you also get access to:
The SDK has support for both Unity and Unreal.
These videos shows the capability of the AR-system: