I'm not sure whether this has already been discussed, but it is possible to reach to your Google Voice number via a SIP connection. I just checked the logs of my VoIP adapter and got the IP address, then used the speed dial feature of my adapter to dial the URI.
Interesting found. I believe you can configure asterisk with a dialplan context to dial out. -- Mazilo always prays for FREEBIES! US Phone: +1-678-601-0907 UK Phone: +44-703-194-2574