Not sure if this will help anyone but I'm sure it might help someone.
Found this while surfing the net could be helpful
Google Voice + Gizmo + Gtalk = VoIP
Here is a quick how-to for setting up a Google Voice/Gizmo/Gtalk
solution to enable people to call you on your PC at no charge (at least
no charge to you, long distance charges would still apply if your GV
number isn’t local to them.)
First of all you need to have a Google Voice number. The reason I say
that this is first is because it takes the longest to aquire. So sign up
now if you haven’t and while you wait for your invite you can finish
the rest of the steps and be prepared to make it all work together in
the end. Goto: Google Voice and sign up. We will wait.
Ok good, now if you haven’t actually signed up for a Gmail account
(or any Google service) you will need to do that and then download
Google Talk . With that running on your computer you will be able to
answer the incoming calls from your GV number. But oddly enough, Google
does not yet support calls going straight to Gtalk. That is where the
SIP (Session Initiation Protocol) client Gizmo comes into play. It will
act as the bridge between GV and Gtalk.
So once you goto Gizmo 5 and sign up for their service. Then in
setting simply choose to forward all calls. Mark your destination as you
Google Talk account. (We are almost done now!) So your Gizmo account is
setup to forward your calls to Google Talk, your Google Talk is running
on your computer and available for use. Since it is open, click
“+add” to add a new user. Then add “service@gtalk2voip.com”
(without the quotes of course) so that when the first call comes through
it wont have to be slowed down with useless button clicking of
acceptance. Now we wait for your GoogleVoice invite.
When the invite comes, pick a phone number that you really want to
keep. You can be creative and pick (area code) I-am-cool, or as some
people have done (area code) x-mm/dd/yr. Whatever number you choose,
know that it is yours and can not be changed (at least not at this time,
who knows what the future holds.) Once you get your number setup, you
can click settings and add additional phones. Choose Gizmo as the phone
type and enter your SIP number. (Probably starts with 1747…) and let
it verify. When GV calls, your GTalk client should ring and (as long as
your speakers work) you will hear it tell you to enter your verification
code. Type the code into the chat window and viola, your calls now
forward to any computer that you log into Google Talk with.
Here's the link too
http://news.netapex.org/?page_id=151