Yes. Lots of posts on the forum. Basically you disconnect the phone company's wire coming into the house and then plug the OBi's PHONE PORT into the walljack, which then powers the entire house. Or, using a wireless phone base you can power it which then powers all of its handsets.
No. Google Voice, and VoIP in general, does not reliably transmit the tones needed. Most alarm companies will not agree to utilize VoIP lines for transmission of alarms.
You can get an internet-based transmission device (doesn't work when the internet is down) or a cell-based transmission device (costs more per month or you have to keep minutes filled).