So ... I got a sip client to work natively (PJSIP) ... there's only one problem, it doesn't detect any audio devices. However 'aplay' seems to have no problem playing an audio file.
Anyone think of anything? I've included the cross-compiled pjsua app if anyone wants to play with it. Either scp or winscp the uncompressed program.
The manual for pjsua is here.
I also have compiled versions for windows and linux-686 upon request.
You'll need a SIP account to really be able to use it.