You need to create a script that sends the push notification to one of those services (for example as a pre-queue script or when a download finishes) and activate that script in sabnzbd. See the sabnzbd wiki for more information on pre-queue scripts and user scripts.
Once you receive such a push notification on your iDevice you can configure the receiving app to open WhatSAB. Use the following custom URLs:
This opens the downloads tab, useful for pre-queue scripts notifying you about new downloads
Opens the history tab, useful for user scripts notifying you about completed or failed downloads
Prowl: Easy Push Notifications
Developer: Prowl Solutions LLC
Developer: Superblock, LLC
Posted in: About