I have been traveling for the past week so I am not sure when this hit the street or that I am seeing it because I am inside of Google but Google has added the ability to directly contact a business via the Knowledge Panel.
The current iteration that I am seeing drives the user from the linked phone number directly into a hangout screen and is immediately ready to dial the business.
Are others seeing this? I am inside the GooglePlex and no one here seems to know about the feature.
Here are the screen you see when you click on the phone number in the knowledge panel:
There are still some very weird interface quirks. For example if you have any problem that prevents call completion you are dropped into the Hangouts interface and given the option to fix settings. However once fixed there is NO way to complete the call without exiting and starting over.
Google Adding Desktop Hangout Calling to Knowledge Panel in Search & Local Finder? by Mike Blumenthal