You might try VoiceMac from http://mrgeckosmedia.com/applications/info/VoiceMac http://mrgeckosmedia.com/applications/info/VoiceMac . I've not used their SIP su

You might try VoiceMac from http://mrgeckosmedia.com/applications/info/VoiceMac http://mrgeckosmedia.com/applications/info/VoiceMac . I've not used their SIP support extensively, and it's primarily aimed to be a Google Voice client, but it might suit your needs. I also don't know if the version on the page is the latest beta, or simply stable. The developer has been quite responsive to bug reports, etc.