ServiceNow Notify is a great feature that provides additional communication vehicles to the platform via SMS and voice; the datasheet can be downloaded here. Included with this plugin is Notify on Task which provides the ability to send an SMS message and initiate a conference call from any task within your instance. This includes incidents, problems, changes, and any table that extends task. The only issue is out of the box it only works for individual users and you cannot leverage groups, which is a common requirement.
Recently posted on Share is an update set that extends Notify on Task that adds the ability to send SMS messages and initiate conference calls to groups.
This update set adds a Groups section at the bottom of the popup as show above. If On-Call Scheduling is enabled in your instance, you can also elect to only include the current on-call person for the selected groups versus all the members of the group. This option will not appear if On-Call Scheduling is not activated within your instance. Since group managers may not always be members of the group, there is an option to include the group manager as well. Duplicates are automatically removed with the out of the box code so users won't receive more than one message or call.
Note: It is important to note that several out of the box components are being modified with this update set so please be aware of this as you upgrade your instance.