Many people use Google Voice as their primary method for communication, but the app isn't great and you can't use Voice SMS messages outside of it. Just 20 days ago, we were reporting that Koushik Dutta announced Voice Plus, an app that allows you to use your Google Voice account with just any SMS app from the Play Store instead of the very limited Google Voice app, Google is yet to merge Voice into Hangouts, so for the moment, this is the best solution for Google Voice users, at least those who are running CyanogenMOD on their phones.
For those not familiar with Dutta's work, he's the Android developer famous for the Clockwork Recovery solution and apps like ROM Manager and Helium (which I still think Google should just buy it and merge it into Android as it's flawless).
CyanogenMOD is famous for creating solutions to common problems and when they work, they just merge it with the source code for the ROMs and offer it to everyone by default and for Google Voice users, this is just what they've been waiting for.
The app, formerly known as Babel and now Voice Plus, has been merged into CyanogenMOD as reported by both Dutta's and CyanogenMOD's Google+ respective pages and will be available in nightlies for CyanogenMOD ROMs from now on, meaning that you won't have to do anything to integrate it like before, just download the Google Voice app, sign-in to it just once and you're done, every SMS app will be able to handle Google Voice SMS messages, both first-party Messaging and third-party apps like Chomp SMS, Go SMS, Handcent or any other one that you might like.
Google hasn't been paying attention to the Google Voice app but I really don't think we'll have to wait too much for Google to integrate Voice into Hangouts, it doesn't make sense for Google to keep maintaining the Voice app with all of its issues when they have a great app like Hangouts already out there, I guess they're just finishing the migration.
It's obviously not going to be announced today, so if you're running CyanogenMOD, you might as well give it a try, it's not like you have anything to lose.