[PD] sip voip external ?

[marco at metm.org]

I would like an external which initiates a voip sip connection and
allows one to send audio from pd to a phone (or ten phones actually).

I am wondering if such a thing exists.  I am just getting started
thinking about making a small project to code this up, but I think it
may be difficult, I need to think about having the audio encoded with
the correct codec gsm or ulaw, as well as all the sip connection
handling (I think that libosip0 handles the connections, but I don't
know about the codecs).

My other idea was that it might be easier to modify one of the existing
sip clients like linphone, or kphone to accept audio from jack, and use
jackd to make the connections from pd sending audio to the sip client.
(Also, started looking at asterisk of course, it has so many functions
it may already do what I want for all I know :)

Anyway, I thought somebody here may have been down this path, so 
Thoughts? Ideas?

Thanks,

-- 
Marco