Free North American calls and incoming calls on your Android phone.

You will need

• a google voice account
• IPKall number (will explain how to get it)
• a SIP provider (will explain how to get it).
• GVcallback app

1. First get a SIP provider. Some of the suggestions are http://sip2sip.info/ and http://sip.antisip.com/account/register.php. Both are free, but I have not used it. What I used is voipraider, but may need to spend $5 to get the connection activated (you can use the $5 to make calls thru out the world).
2. Download CSIPSimple and register the SIP account created the above step. Make sure that the SIP registration in CSIPsimple is successful and active (the account will show as green and will show in the notification area of Android).
3. Now create an account using IPKall. Provide the SIP information from step 1 and you will be given a free US number. (What IPKall does is forwarding calls to the number (free US number) to the SIP account. If the SIP account is online (in Android), you will get the call. This way you can get free incoming calls on your Android.)
4. In the google voice webpage, add the IPKall number from step 3 (Tip: If Google voice does  not allow you to enter the IPKall number because it's already used, create a new IPKall number). Install GVcallback app on your Android and select the number just added as the number for call back.

That's it. If you dial somebody from your Android phone, an option will come up to dial using GVCallback. Just select that option and you will receive an incoming call. Once you accept the incoming call, it will dial the outgoing call. You can use this method to receive and make calls only using Wi-fi (no need of phone connection).

I am writing about this method so that you know such an option exist. It is your responsibility to understand the terms and conditions set forth by your phone company/google.