In this mode, your phone will look for the Nold Open device in the background. If it founds it (you are in Bluetooth range), a notification will pop-up on your phone, so you don't need to start the app to select a key, you can interact with Nold directly from the notification. Optionally, it can open the door at the same time you see the notification on the background.
To setup auto-open and notification, go to your device settings and check the Allow notifications option.
You can setup notifications in two ways:
When i arrive
In this mode, you'll see notifications only when you are arriving from a distance and it won't appear again during your stay. This is useful for garage doors and gates for example, so it won't open by accident while you are moving around the house.
In this mode, you'll see a notification every time you get close to Nold Open. You can configure the range, so it will only trigger the notifications when you are really close to the device. This is useful for office doors for example.
For both methods, you can turn on Background open. If this is turned on, your door will open at the same time you see the notification on your phone.