QBZappy's comment caused a thought to occur to me.
The OBiAPP program provides a "shim" between the OBiTALK network and a standard softphone. Unfortunately, in its present form it is Windows-only software. I'd love to see it ported to Unix/Linux but I have the distinct impression that's not going to happen anytime soon. But anyway, my point is that if a softphone can connect to the OBiTALK network via the "shim", then Asterisk should be able to as well. Basically all you have to do is set up Asterisk to pretend it's a softphone, which is what you're in effect doing when you set it up to work with several commercial VoIP providers. If OBiAPP would run under Unix/Linux, this would be doable. Now, granted, you could set up a Windows box and run the OBiAPP program and then connect to that, but that's going to cost you a whole lot more than a $30 OBi100 which will be out in a couple of weeks and give you the same functionality, plus an FXS port for one of your Asterisk extensions, plus the possibility of a gateway to a Google Voice account (especially useful if you're still running pre-1.8 Asterisk) or another SIP account.
But assuming you really want to connect directly for some reason, as I noted in a previous post (I think), I was able to get OBiAPP to run ONCE on a Mac under WINE (not CrossOver), and it sort of worked, thought there were definitely issues. But when run that way it wasn't reliable and I couldn't get it to work again, though I didn't put a lot of effort into it either. I'm assuming that it works as intended on a Windows box. It might also work in something like VirtualBox - as I say, I really didn't put any significant amount of effort into it.
Also, just so you know, the Google Voice integration in PBX in a Flash comes in two different flavors, one of which relies on channel drivers included in Asterisk version 1.8, and the other on a somewhat kludgey callback system that works in earlier versions of Asterisk (I wrote a couple of how-to articles for those who wanted to accomplish it on Asterisk/FreePBX systems that don't run PBX in a Flash, so I'm pretty familiar with the techniques). The point is that in neither case did Google Voice offer any assistance whatsoever. And the Skype support either depends on using a commercial Skype channel driver ($66 for a single channel, last time I looked), or a really kludgey method that involves actually running a Skype client on your Linux box (I installed it just to see if I could get it to work, and it did, but it was such a resource hog that I took it down again). But again, I'm pretty sure that Skype didn't cooperate with the PBX in a Flash folks in any way, though they may have had a hand in the commercial channel driver used with Asterisk.
I'd be happy if the Obihai folks would release a Linux version of OBiAPP (if they release a Linux version then either the MacPorts, FINK project, or Rudix people will likely port it to the Mac, if Mac users want it, although in my case I'd just run it on a local Linux server and connect to it from my Mac). But to me personally, that's not a real high priority compared to a few other things I'm waiting to see (although it would definitely be a neat thing to play with). But if we can get even that much support for Asterisk, I think we should be happy. And keep in mind, in a couple of weeks you can buy an OBi100 or OBi110 for a lot less than that single channel Skype license, and you'll get a whole lot more value from it (just my personal opinion).