I did a search for "Hangouts" and found nothing, so I assume this might not be known by the greater community.
Google recently upgraded the Google Chat/Talk interface on the Gmail web page - and they've created an extension for Chrome that provides incoming call functionality.
Option 1:
1) On the "Chat" section on your Gmail page, click on your own avatar/icon, and choose "Try the new Hangouts".
2) Call your google voice number from an external number, and watch as your obi phone and your PC ring.
Downside: The original interface with the dial pad (used to make outgoing phone calls) will be gone. Google says they're going to integrate this as the new interface matures.
Option 2:
1) Go to the chrome extension store, and search for "Hangouts" (not Hangouts Call), and install it.
2) Call your google voice number from an external number, and watch as your obi phone and your PC ring.
Upside: your original google chat/talk interface in Gmail remains, so you can continue to make outgoing calls.
One thing to note about Hangouts... when you receive calls and accept them, Google opens a new Chrome window - showing the call. If you close that window the call will disconnect. Further, if the caller hangs up, the Hangout window will remain open. You MUST close this window to be able to accept additional phone calls. It's a bit of a pain, but if you get in the habit of always closing the Hangout windows, it should be a simple fix.
The extension of Chrome for incoming call is very useful for fast call facility. The ringing PC and OBI system is excellent way of quick calls.