As you already know, Google Voice already gives you FREE outbound calling in the U.S., but the missing piece of the puzzle is free INBOUND calling. Well, Gizmo5's beta service called Gizmo Voice is the final piece to the puzzle. Gizmo Voice lets you take full advantage of the messaging and calling services of Google Voice combined with Gizmo5's support for any SIP device. Thus, in addition to the free inbound and outbound calling, you also can take advantage of Google Voice's free voicemail and free voicemail transcription.
With Google Voice + Gizmo Voice you can make and receive U.S. calls without any monthly or per minute fees. This is a game changer! SIP termination providers surely aren't going to be happy about this deal. How can they compete with free?
With Google Voice as your single centralized/unified number, their advanced call routing rules and now free inbound/outbound calling, Google Voice might just dominate the telecom world just as Google has dominated the Internet. How long Google will keep this "free" remains to be seen, but here's a step-by-step recipe to get free inbound/outbound calling:
1) Get a Google Voice account invite here. Might take a month or so if you haven't signed-up already. Google likes doling out accounts slowly for whatever reason.
2) Download the Gizmo5 client here
3) Add your Gizmo5 number as a forwarding phone number in your Google Voice account.
4) Designate another forwarding number in Google Voice that points to a SIP-based DID number mapped to your SIP-based IP-PBX or it can be your Gizmo5 number as well. Of course, the calls are free so the area code of the DID number doesn't matter.
5) Add your Gizmo5 SIP credentials to a SIP device (softphone, IP phone, IP-PBX trunk, ATA, etc.) so you can make/receive calls via Google Voice.
- SIP server / host=proxy01.sipphone.com.
- Username: Your ten digit Gizmo number and country code [1 ### ### ####] with no spaces
- Password: your password
- (optional - if having NAT / one-way audio issues - STUN server: stun01.sipphone.com:3478)
Oh wait, there is! Both fring and Nimbuzz support adding SIP credentials. I've used the Nimbuzz iPhone app a few times to register onto our corporate IP-PBX using SIP. The only downside with Nimbuzz's SIP app is that after it initiates a call, there is no dialpad for transmitting DTMF touch-tones. Thus, no traversing any IVRs/auto-attendants. Still, it's free... Same with fring.
Lastly, if you use Asterisk, you should check out Nerd Vittles' recipe for enabling your Asterisk-based PBX to make/receive free calls leveraging Google Voice + Gizmo5.