Don't worry about missing important notifications. While you're in any VR app, you'll see a notification when you have an incoming call, message, or upcoming calendar event.
To receive notifications while in VR, you need to pair your phone with Vive
first. To find out how, see Pairing your phone with Vive
To receive or open the notification, press the System button.
If you choose to ignore the incoming notification, you can always check it later on the Vive tab. For details, see Checking your notifications.