Intentional necrobump to document a solution to a problem aided by this thread:
My goal was to use one Google Voice number/account to simultaneously ring two Obi devices, an Obi100 and an Obi200. This combination of devices will not simultaneously ring by default.
I registered the 200 first with no issues. Inbound/outbound/ring were fine.
I registered the 100 second. Outbound calls were fine, but this phone would not ring.
Solution: Set up Google Voice on each device using the standard method, then use the settings changes indicated by @azrobert, on each device, with my tweak:
Voice Services -> SP1 Service -> X_InboundCallRoute: ph,pp(xxxxxxxxx)
Voice Services -> OBiTalk Service -> InboundCallRoute: ph,pp
Whereas the xxxxxxxxx is the number of the OTHER device.
The phones now simultaneously ring, and the first one to answer connects the call.
Cheers.