Third-party apps for Google Voice have six months to live. Google said today that it is ending support for apps that "are making unauthorized use of Google Voice" by providing calling and SMS services. "These apps violate our terms of service and pose a threat to your security," said Nikhyl Singhal, director of real-time communications, in a post on Google+. "So we're notifying these app developers that they must stop making unauthorized use of Google Voice to run their services and transition users by May 15, 2014."

Separately, Singhal said that today's update to the app will not allow users to send SMS messages on Hangouts with their Google Voice numbers. Sprint customers are the exception, as the company allows users to maintain a Google Voice number as their primary phone number. Singhal said that Hangouts would support sending from Google Voice numbers "early next year." Google is also working to enable Google Voice for phone numbers outside the United States and to enable MMS messages, the company said. Signhal once said that "Hangouts is the future of Google Voice," but it's clear that getting there will require resolving several key issues with carriers first.