To build an app for Apple's new Vision Pro, apply for the latest Vision Pro Developer Kit. Current iOS apps will have a path to port over to visionOS.
iOS already has an ARKit framework for utilizing the iOS device camera and sensors. The main classes here are ARSession for configuring capture and ARView to render. There is also SensorKit to expose device sensors.
What hardware capabilities will be exposed by APIs and frameworks have not been publicly detailed. There are a number of new hardware systems such as the LIDAR sensor, Vision Pro's EyeSight, the main augmented reality display, and the various new input gestures sensors.