Unfortunately, Google Voice doesn’t yet support forwarding to international numbers, which, for someone like me, living in Spain but with considerable interests in the US, is quite a bummer. (What I particularly like about Google Voice is its call screening facilities.)
To work around this limitation, I have Google Voice forwarding to my US SkypeIn number.
This works well when I’m at the computer, as I can answer my Google Voice calls directly in Skype. But what about when I’m not at the computer?
One of Skype’s preferences is forwarding, and I have it configured to forward unanswered calls to my iPhone. While this works fairly well, a parameter I’m still fiddling with is the time after which Skype considers the call “unanswered” and does its forwarding.
If you set this value too small (like “1 second”), then you don’t have enough time to answer Skype calls when at the computer. If you set it too large (like “10 seconds”), then your Google Voice call will timeout and get dropped long before Skype has time to forward to the iPhone.
Presently I have this value set at “4 seconds”, which seems to be a good trade-off.