Yes, but the real extra that Tablet Talk has is the ability to answer phone calls you receive on your phone - WHILE WORKING ON YOUR NEXUS 7.
Here is the feature description from the product Help:
"By default, Tablet Talk notifies you of incoming calls, which you can silence or mute from the tablet. You can adjust the vibrate and ringer setting for the caller ID popup, or disable it altogether.
By popular request, the app also now has the ability to answer and dial calls from the tablet. These features were designed for users with Bluetooth headsets who wanted to be able to control phone calls from the tablet. It is possible to use a Bluetooth headset and Tablet Talk on your phone at the same time.
NOTE: The new phone calling features are intended for use with a headset connected to your phone. You can also enable your phone's speakerphone from the tablet during a call. Due to limitations of Android, the tablet's speaker and mic cannot be used for active calls on your phone."
So, the configuration is ... You have a BlueTooth for the phone, and you can dial and answer phone calls ... without ever leaving the Nexus 7.
I don't know about Google Voice, but that Tablet Talk feature seems pretty damn cool to me.