How can I make/receive Google Voice calls in Mountain Lion?

I use Google Voice as my main line now adays. However, having to leave Google Chrome open and logged into Gmail is getting in my way...

I was wondering if anyone has a way to get these calls to go to a VOIP app that is installed on the computer. Does such software exist?

The telephone app in the app store is a great one to use, i'm using it in mountain lion and it works perfectly, was by far the easiest softphone I've ever set up. http://itunes.apple.com/nz/app/telephone/id406825478?mt=12

Use Fluid to create a site specific browser, log into gmail/gtalk uisng the mailbox of your google voice account. Then convert the SSB to a Menu item. That way it stays active and you never lose track of the soft phone - It's always on the menu when you want to dial or answer a call. Oh, you need to add your google chat as one of the phones you use with Google voice.

If you use Google's browser, Chrome, then you can install the "Chat for Google" extension.

Beside installing the "extension" through the Google Chrome Web Store it requires no configuration because it automatically signs you in unless you're already signed into your Google Account.

It only runs while Chrome is running, which is disappointing, so if you close Chrome that service will quit as well. But if you use Chrome as your primary browser I suppose that doesn't matter.

Also, it displays a window of contacts from your Google account, acting as a chat service. You can close the contacts list, but I'm not sure if you can silent the incoming chats (which is desirable if you use Messages for your chat client).

I happily receive and dial calls from the application though!

The Telephone App for OS X does work with both Sipgate One and CallCentric. http://www.tlphn.com/ or Via the Mac App Store. You'll need to set your Google Voice number to forward to the SIP number you register with one of those SIP providers. It is a very good lightweight VOIP (softphone) app and it is free. Blink used to be free but now it is no longer.

A separate but quality non-free notification ($4.99) utility for Google Voice and OS X is GrowlVoice, http://www.growlvoice.com/. It is quite similar to what Google offers for Chrome as the GV Extension (on Chrome Store) but seems to play more seamlessly with OS X and Growl notifications. And it has the added benefit of always running in the system bar, so if you close Chrome you'll still see SMS notifications. Telephone.app doesn't to offer this though, which would be nice, as a sort of integrated system bar icon to know when your GV/SIP phone is ringing.

A third alternative would be to pay Skype for incoming/outgoing forwarding. Skype "Premium" is $30 per channel for unlimited calling (in/out) so a total of $60/year to use it in both directions. Skype of course is a bit larger and more cumbersome of a program and also has pretty bad contact management integration in OS X.