Not that I have a solution but I am just curious how you plan to use Gizmo here:
1. As client to receive calls to GV #.
2. As client to call out from your GV #.
3. As client to call out from Gizmo.
3. Just as a dumb termination for your GV #.
In my case I attached an ATA for Gizmo/GV with a phone connected, so I can call out and receive calls on the phone, rather than on PC, but if you need chat, then you do need a PC...