it’s not completely ideal yet, but it works. here’s what i did:

1. activate your google voice invitation & pick out your number.
2. download truphone to your iphone & activate your account
3. sign up for a free gizmo account online
   • after activating your gizmo account, click on the My tab
   • choose to Forward All Calls using SIP
   • enter YourElevenDigitPhoneNumber@truphone.com as your SIP number
   • your gizmo number is just below that; copy it, we’ll need it in a minute
4. go back to google voice
   • click on the settings link in the top right, then click on the phones tab
   • add your gizmo number as a new phone
5. visit google.com/voice/m on your iphone—you can even add it as a bookmark on your home screen
6. enter the number you’d like to call & tap call, choose your gizmo number when prompted
7. press your home button & quickly open the truphone app
8. answer the call and wait for google voice to connect you
9. smile smugly knowing that you’re making a VOIP call on your iphone

my iphone isn’t jailbroken, so this will only work on a wifi connection. ideally it would all be a bit smoother, but i can put up with the extra steps knowing that i’m making a really high-quality FREE wifi call.

i didn’t come up with these directions, but really compiled them from several sources. i hope it helps; it works great for me.

take that, at&t.