SIPphone announced that it has secured US $6 million in funding to expand its Session-Initiated Protocol (SIP) standard service to non-PC devices such as adapters, routers, WiFi handsets and dual mode mobile phones.

SIPphone is the developer of the open-source Gizmo Project, a peer-to-peer VoIP network. The company provides free VoIP Gizmo Project software for Macintosh, Microsoft Windows and Linux computers, which enable free calling and IM worldwide using any Internet connected computer.

"The release of Gizmo Project has driven over 400,000 registered users to our PC-based service, but our goals go beyond free calls between PCs," said SIPphone CEO, Michael Robertson (pictured). "We want to seamlessly link the Internet and the traditional calling world of landlines and mobile phones, and that's becoming possible as low cost SIP-based devices such as dual-mode mobile phones and WiFi phones become a reality."

The financing round was led by New York-based venture firm Dawntreader Ventures and is the first external funding for SIPphone. Joining the board of SIPphone is Dawntreader managing director Edward G. Sim. Private investors from Michael Robertson's previous digital music startup MP3.com also participated in the funding.

SIPphone will use the investment to expand its VoIP platform to portable devices that do not require PCs to make or receive calls and promote adoption of the open standard auto-provisioning system plug-and-dial. The company noted that its San Diego-based headquarters is expected to triple in size over the next year with hiring primarily in business development and engineering.