I don't know enough about the Cisco 7970 to advise you on that particular SIP phone. If you would like to set up your OBi ready and try it out using a free softphone from your PC, then I advise the following:
Softphone: Use PhonerLite – it's free, easy to configure, good debugging – a useful test tool. Set it to call without registration; proxy/registrar set to OBi sp2 address and UserAgentPort (for example 192.168.1.10:5061). Give yourself an easy User Name, maybe an eight digit number. Set Network > Local Port to a value that will not clash with other devices, say 5470.
OBi110 settings for sp2:
Service Providers -> ITSP Profile B -> SIP -> ProxyServer : 127.0.0.1
Service Providers -> ITSP Profile B -> SIP -> X_SpoofCallerID : checked
Voice Services -> SP2 Service -> Enable : (checked)
Voice Services -> SP2 Service -> AuthUserName : (any letters or numbers)
Voice Services -> SP2 Service -> X_RegisterEnable : (unchecked)
Voice Services -> SP2 Service -> X_ServProvProfile : B
Voice Services -> SP2 Service -> X_UserAgentPort : 5061
Voice Services -> SP2 Service -> CallerIDName : Whatever
Voice Services -> SP2 Service -> MaxSessions : 4
Call from PhonerLite to OBi > anything@192.168.1.10.5061
Call from OBi to Phonerlite > sp2(anything@192.168.1.13:5470)
(Put this in a OBi Speed Dial. It assumes that the PC is at 192.168.1.13)
There's lots more to be said about Digitmaps and InboundCallRoutes etc to fork calls coming into OBi to the softphone and giving the softphone access to the OBi Auto Attendant and direct outgoing calls.
If you get this setup working and sort the DigitMaps, InboundCallRoutes etc to work how you wish, then you just have to make you SIP phone act the same as your softphone