babobi, I looked at a lot of different services, just about everything I could find on Google, and finally settled on NetTalk. They currently have two devices, one that can use WiFi to connect, the other requires a wired connection but is US$20 cheaper and competitively priced with the OBi100. I went with the cheaper one because I don't really cotton to the idea of doing this by WiFi.
You can probably buy either at your local electronics megamart. I picked mine up at Fry's because I like their return policies.
The NetTalk devices come with a year of free service, then is $29 per year after that, has caller-ID NAME, can do a version of emergency calls, you can disable their Voicemail if you don't want it, and you get unlimited free calls to the US and Canada. (I've never called overseas in my life.)
It does take an unseemly while to port my number away from GV to NetTalk, (like up to a month -- but so does everybody else nobody I talked to could do it any faster), but when you register the NetTalk box, you get a new phone number, and have no choice about that.
Then you request the port and wait. Meantime, you can forward your GV account to this new number, and that will get you back your caller-id NAME (as well as working with touch-tone services and doing away with all the other problems I'm having with GV.)
You can log into your OBi box and make various parameter changes, but you can't do that with the Nettalk box. They won't tell you the login and don't want you messing with the parameters, so that you can't even, e.g., assign it a static IP address, it has to use DHCP.
Like the OBi box, the Nettalk box doesn't require a computer, just the router/gateway provided by your ISP, to work. The Nettalk box draws power from a USB cable. You *can* connect it to your computer via said USB cable, or you can connect it to your gateway via an Ethernet cable and just use the USB port for power from a wall plug, as I do. Physically it's about the same size as the OBi. It will give you enough juice to ring phones throughout the house, if you're set up that way.
I haven't found a significant downside to it so far.