Could someone with an N900 please test the following and see if it should be added to the summary:

Receive and Send calls with Google Voice using only Data, not Voice Minutes

Google Voice Supports connecting calls made to Gizmo/SIPphone accounts. You can register for an SIPphone account here:

https://my.gizmo5.com/gizmo5/app?class=MySip;proc=start

Once you have that set up, you can add the SIP account to the N900. Follow the directions here:

https://my.gizmo5.com/gizmo5/app?class=MySip;proc=start

Finally, go to the Google Voice website and add your "747" number to the account. If you are in an area with strong 3g coverage or always around wifi, it may be wise to disable your normal phone number from call forwarding, that way, you don't get two incoming calls at the same time. When you receive calls, you will only be charged data. To send calls, you can use the Google Voice website and select "send to Gizmo". Again, you will only be charged for data.

---

I kind-of prefer this solution to the myfaves one. First of all, you can buy the individual 300 plan rather than the MyFaves 300 plan and save $10 per month. Also, I remember the T-mobile website saying that only certain phones supported MyFaves - is this incorrect or does the N900 have some sort of MyFaves software barried in it?