While we all sit back and wait for the integration of Google Voice into Hangouts on our Android devices, it's important to revisit the fact that any unauthorized third party Google Voice applications will end up coming to an end in the near future. Many users may not use third party Google Voice apps anymore or may have already found other alternatives for their VoiP needs, but we know that there will still likely be some users out there that might have forgotten about the shutdown of those third party apps soon.
Google mentioned in the past that this would be taking place so users shouldn't be completely alarmed or surprised, it was brought up at least once before. If you have missed it though Google's notice stated that all unauthorized third party Google Voice applications would be shut down as of May 15th this year, which as one would have it is in a short 20 days. That basically means you have less than a month to find another app to use that might be authorized-if there are any-or find a completely different VoiP alternative through different means. Who knows Google may end up surprising everyone with Google Voice integration out of the blue, but the announcement that it would be integrated into Hangouts in early 2014 is pretty vague and only lets us know that it's coming but gives no exact date, so we would suggest finding a solution to the shutdown in the meantime and not waiting around for when you can use Hangouts for this particular function.
Google's whole initiative to shut down unauthorized apps is according to Google, in direct correlation to their betterment of security efforts, stating that unauthorized Google Voice apps hinder this security and Google's ability to make Google Voice a secure use feature for all. Google's Nikhyl Singhal made this announcement back on October 31st, which has given ample time to many users to find a switch. If you haven't yet found something to replace the use of services like Groove IP or other apps, you still have a little bit of time to do so. For those who have been using these types of apps simply to get some free calling at the expense of data usage, you could always try to utilize Facebook Messanger's calling feature which also uses up data to make voice calls, although I have never personally used it and can't speak to how well it works.