A bit cumbersome but if you can sign up for an IPKall number (that is usable with GV--as over the years people use it with GV and many of it gets tied up even when recycled) and Localphone account. Point the IPKall number to your Localphone account (you do this under the SIP URI (after logging into IPKall) using the Localphone # 7841212 then after the @ put
localphone.com) then add the Localphone account to your OBi device under an available SP slot--then add your IPKall DID number to GV so it can verify. Once that is done, you will have the option when recording a new greeting in GV to use the IPKall DID which will then ring to your OBi, if properly set up.
Another route similar to the above is to get a free CallCentric NY number and set up an account outside of the the US (as you are currently--so you don't have to pay for the 911 fees). Once you do that, add the CallCentric account to one of your open SP slots in the OBi device. Finally, add the CallCentric number to your GV and once verified, you can do the same call recording using the CallCentric DID number.