From VoIP.ms Wiki
Vimphone  is a free app (GPL) which allows Android users to make inexpensive calls using VoIP.ms (or any SIP-compliant provider) and a wi-fi connection.
While using an Android handset gives the "look and feel" of calling from a cell 'phone, there is no requirement that the phone be subscribed to a mobile telephone provider. Calls placed over wi-fi incur standard VoIP.ms rates, not the far higher cell phone rate.
The Vimphone application is a free download at the Google Play store. When installed, it must be configured for your VoIP.ms account before you can make calls.
Press the [menu] key, then Settings -> Account setup assistant -> I already have a SIP account.
The application will prompt for "username, password and domain".
- Username: 100000 (your VoIP.ms username)
- Password: ******** (account password)
- Domain: atlanta.voip.ms (one of our multiple servers)
Press 'Apply', then return to the main screen. A green dot and the word "Registered" should appear at the top of the screen if registration is successful.
At this point, your Vimphone is ready to place calls on the VoIP.ms network.
If you intend to receive calls, you may wish to have Vimphone automatically log into VoIP.ms on startup:
Press the [menu] key, then Settings -> Advanced -> Start at boot time.
- The Vimphone app does not send caller name for caller ID purposes
- The Vimphone app does not do dial translations (for instance, to add home area code to seven-digit calls)