This is how you can get it to work:
Use eg a contact, motion sensor etc and expose it to HomeKit. Configure the eg contact in HomeKit to send a push notification to your device when it’s status changes.
And now comes the magic 
Set up the guided access in iOS for your openhab app or browser. If now the iPad receives the push notification from your sensor, the screen will light up, but the notification won’t show because of the guided access.
Looks like this:
