Since the beginning of this year, OBiTalk has had at least two unplanned outages...
Reliability of the service is irrelevant with respect to this feature request. By the time the feature is implemented, the reliability record may be completely different. (If you want to advise against relying on OBiTalk in the short term as a footnote, then fine.)
Unfortunately, the proprietary nature of the protocol makes troubleshooting very difficult; most of them simply gave up and now use SIP or another alternative.
(I don't have any knowledge of the protocol; this is based on observations of RTP being relayed via OBiTalk servers.)
Anyone know why they wasted their time reinventing SIP?
It should be in all of our best interests to encourage them to peer with other SIP providers, accept inbound calls (if the user desires) to OBiTalk servers via SIP, and eventually replace their proprietary protocol with SIP.
On those grounds alone this is a worthy feature request.