Default Google Now Text Command / Google Voice integration

does anyone here know how to integrate Google now with the Google Voice application for sending text messages? When I tell people now to send a text message, it comes back and says that it is unable to perform this function. I am assuming it's doing this because there is no default SMS application for the Nexus 7. How can I force this command to go to Google Voice, and therefore link send a text message command to that application? Is there an intermediary application required to make this work? Thanks for your help.