Correct, the Obi is causing the google chat session to be active. That is the reason to move the number to another unused gmail account where the chat status would not matter. The old gmail would not have a google voice number anymore.
I have transferred several google voice numbers to new gmail accounts without a problem. The new process actually takes place immediately.
I even found out that it may be possible to bypass google's voicemail by using the transfer.
Do this from a computer that already has the gmail/chat voice and video plug in installed. Do not have your gmail or google voice open in any browser.
1 - set up a new gmail account
2 - enable chat for the new gmail account
3 - set all mail from the new gmail account to forward to your old gmail account and sign out.
4 - transfer the google voice number to the new gmail account
http://support.google.com/voice/bin/static.py?hl=en&ts=1378507&page=ts.cs&from=1378507&rd=25 - DO NOT MAKE A PHONE CALL PHONE FROM THE NEW GMAIL ACCOUNT.
Your google voice number will now be associated with your new gmail account and calling in and out from your Obi should work normally when set up with your new gmail credentials.
***It is possible that calls to your google voice number will ring continuously and not be picked up by your google voicemail. This would allow you to use a home answering machine connected to your Obi, or the voicemail from another forwarding phone. If that happens, and you like it that way,
never open the new gmail account again. If you do want google's voicemail to pick up your calls like it is suppose to work, then go back to the new gmail account and make that phone call.