If you have an old Android phone laying around and you want to be able to use it for phone calls, you can setup Google Voice WiFi Calling With Sipdroid. There are a few walkthroughs around, but none were really easy to follow or complete.
1) Google Voice
– First step is to get a Google Voice number. Head over to http://www.google.com/voice. Make sure you’re signed in with the Google Account you want to use. – Once you have your number tied to your Google account, head into Settings and make sure you have it set to Forward All Calls To Google Chat. – While still in Settings, go to the Calls tab and turn off Call Screening. – Special Note: Since Google will probably block the request from Sipdroid to link with your Google Account, head over to this Google Security page and allow access to less secure apps.
2) On Your Phone
– Download and install the Google Voice app from the Play Store – Log into the Google Voice app and go through the setup steps – Download and install the Sipdroid app from the Play Store
3) Setup Sipdroid App
– When you first run the app, there should be a button at the bottom that says: Setup PBXes with Google Voice…click that button. – Verify your google voice account email is correct and enter your google voice password below. Disclaimer: You will be sharing your Google password with pbxes.org. – Click on Create (or Configure). It might take it a minute or two, but it should link to your Google Voice account with an Ok message.
– PBXes.org Login: If you need to, you can login at pbxes.org with the account name Sipdroid gives you and your Google Voice password. There are some settings you can go through, but the default will work fine. – PBXes Not Linked To Google: Under Trunk on pbxes.org, you can check that your pbxes account is linked to your Google Account. – Starting Over: If you run into any issues and need to start all over, remove both the Google Voice app and the Sipdroid app from your phone. Reinstall both apps. – Trunk Already Associated: If you get an error about the trunk already being associated with an account, log into that pbxes.org account and go under Trunk and remove the GMail trunk. – No Option To Forward Calls To Google Chat: If you don’t have an option to forward your calls to Google Chat, it is probably because you setup Hangouts right away. To fix this, log into your GMail account and click on your name in the chat area in the lower left column. At the bottom of the pop-up window, you should have an option for “revert to old chat”, click that and walk through the steps to change back to the old Google Chat. Then dial a different phone number and hang up. Log out and back into Google Voice account and the “Forward to Google Chat" option should now be available.