DeoVR is the only VR app I've used which doesn't lock the cursor when running. This means that if you have multiple monitors, the cursor can leave the main display and mouse clicks will no longer work.
here's how to lock the cursor in Unity
Cursor.lockState = CursorLockMode.Locked;
or you can confine the cursor to the screen with
Cursor.lockState = CursorLockMode.Confined;