1. I think RonR was trying to cover two situations.
(a) A local set up where all OBi devices and IP phones etc are behind one router. In this situation each address is simply the local IP address allocated by the router followed by the UserAgentPort of the sp service used. Let's say sp2 was used at default settings then: 192.168.1.140:5061
(b) A "worldwide" set up for family and friends. In this case you need to use the public IP addresses of the routers involved (if static) or their dns type names e.g. @cmr.dyndns.org. Again, these need to be followed by the UserAgentPort number. Let's say sp2 was used at default settings then:
anything@cmr.dyndns.org:5061
In (a) and (b) above the InboundCallRoute of sp2 can be used for the normal routing tricks using Caller ID from the incoming call, the same as the service actually configured on it.
2. You cannot use an spX with GV configured on it as SIP protocol is needed to make this work. However, calls into and out of GV can be routed to the spX with SIP on it using the usual call forwarding and InboundCallRoute rules of the spX configured for SIP being used. The DigitMaps etc work the same whether spX has a real service provider configured on it or the fake service provider RonR suggests.
I notice that in a current thread some users are worried about the OBiTALK network disappearing one day. Using this "single-stage dialling using SIP", it is possible to build your own network between friends and family.
This might give some insight to a simpler set up that illustrates some of the points:
http://www.obitalk.com/forum/index.php?topic=4609.msg30203#msg30203I did forget to say in that post that I did have to set Voice Services > SP2 Service > MaxSessions > 4 to get multiple calls working through sp2.