Contact Action Trigger
Create a Contact Action trigger to set an alternative action to be performed on an Address Book Contact's field when you select it in Alfred's Contacts Viewer.
Contact Action Example Use
First, create your workflow; Create a Contact Action trigger and a Run Script or Run NSAppleScript action, containing the necessary script to use your favourite VOIP software.
Go to Features > Contacts and create a new Custom Action for the "phone" field.
When you next press Return on a phone number in Alfred, instead of performing the default Alfred action for a phone number (copying the phone number to your clipboard), it will start your VOIP call.