As the title suggests, Cyanogen Mod will now enable marrying of Google Voice and the default messaging app being used on the phone. If you already have the latest nightly build of Cyanogen that is after July 1st or later, then you can just setup the phone to work that way. The method to activate this feature has been detailed by Koushik Dutta, part of the ClockWorkMod frame.
For this to work the Google Voice app needs to be installed. After that an app called babel-signed is required to be pushed to the /system/app, since a normal adb install won’t work because of permission issues. Once that is done, start the Babel app and authorize the Google Voice app. After this is done, Babel needs to be enabled from the settings and it is all done! From here on forth all of the Google Voice messages will be stored and shown in the default messaging app.
But on the negative side, an messages sent would be sent through Google Voice and would show the Google Voice number instead of the real number being sent. Also, Koushik points out that the name babel will change, thus pointing to this method being a work in progress.