Thanks to you both.
Frunple - Interesting thought to be able to have a "dial plan". Would that mean I could hit a star-something to get a GV dialtone - the rest of the time it could be POTS?
For now I intend to just have a GV phone only, no POTS connection. Maybe in the dead of winter when I get some time I can play with it more.
If your home has a central place where all of your phone lines do home runs, then you can split up the analog wires and make some of them Obi lines and some pots lines.
The basic thing is that the obi has a single analog output. Any incomming call to the obi whether via ip or via the pots input on it, will be output to that one analog line. You can however make each input have its own unique ring so as to know which number is being called in on. You can have two ip services and one pots all with their own rings, but still all the phones will ring.
As far as outbound, you will set a default service (pots, GV, other voip), but there is a code (I forget what it is, it is like ** something) which allows you to select which service is going to place the outbound call if you want to use other than the default. The free GV doesn't do outbound, so you either need to use your pots line, have a sprint cellular line linked to GV, or pay for one of the other voip services.