Push Notifications can be used in most every service OS X Mountain Lion Server can run. Any service that requires Push Notifications will provide the ability to setup APNS during the configuration of the service. But at this point, I usually just set up Push Notifications when I setup a new server.
To enable Push Notifications for services, you’ll first need to have a valid AppleID. Once you have an AppleID, open the Server app and then click on the name of the server. At the Overview screen, click on Settings.
At the Settings screen for your server, click on the check-box for “Enable Apple push notifications.”
At the Apple Push Notification Services certificate screen, enter an AppleID if you have not yet configured APNS and click on OK. The Apple Push Notification Service certificate will then be configured.
The certificate is valid for one year, by default. Administrators receive an alert when the certificate is due to expire. To renew, open the same screen and click on the Renew button.
Enter the credentials for the AppleID again and then click on Renew Certificate button. The certificate will then be valid for another year.