The Linksys PAP2T Internet Phone Adapter with 2 VoIP Ports enables high-quality feature-rich VoIP service through your broadband Internet connection, including providing caller ID, call waiting, voicemail, call forwarding, distinctive ring, and much more. I was using this with 2Talk who have an online configurator for this device which makes it easy to set up. http://blog.2talk.co.nz/pap2t.html
Going for around $50 on TM. Looking for $30. Pick-up is Beach Haven, Auckland or can ship at buyers expense.