In magento xmlconnect_notification_send_all is a core cron job.
What is exact purpose and scope of xmlconnect_notification_send_all cron job?
The Mage_XmlConnect
module is used for managing and configuring the mobile application connected to your website (if you have one).
I'm not 100% sure but I think that cron is used to send push notifications to the app users.
Off topic: If you don't have a mobile app you can disable that module by adding a new file in app/etc/modules
. Call it Zzzz.xml
(so it's loaded last) with the following content
<?xml version="1.0"?>
<config>
<modules>
<Mage_XmlConnect>
<active>false</active>
</Mage_XmlConnect>
</modules>
</config>