To make and receive calls using Google Voice via SIP, you need to run a server that is able to do this 'conversion' for you. I originally tried asterisk as the server, and had nothing but problems getting it to work. Calls would ring my phone, but when I answered it would immediately hang up. Asterisk would crash, and I would miss calls, etc. I finally bit the bullet and configured Yate as a SIP server for Google Voice. I haven't had any issues that the mailing list wasn't able to solve yet (someone even wrote a guide to press 1 to automatically accept incoming calls), and haven't had any crashing issues. I wrote a guide on setting it up if anyone's interested: http://www.tuxguides.com/yate-server...voice-calling/