QuteCom (formerly WengoPhone) is a multi-platform VoIP client. The GUI is Qt-based, and the Video-over-IP engine is based on the eXosip, oSIP, oRTP, ffmpeg, and libgaim projects. The eXosip module is extended by a phApi module, which implements a high-level, easy-to-use call control API. It supports PC-to-PC voice, video, and chat. One can use a standard SIP service provider such as Wengo to be assigned an incoming number, make calls to PSTN/cell phones, get voice mail, and more. In addition to SIP/SIMPLE QuteCom provides IM functionality using libgaim, so it is compatible with all protocols supported by libgaim.
Verona is a portable VOIP toolkit based on eXosip, oSIP, oRTP, curl, and ffmpeg. The toolkit includes a phApi module, which is a high level VOIP API that allows a developer to create voice/video over IP applications in a dozen lines of code. It includes an example of a minimalistic SIP user agent that supports audio and video transmission. The toolkit is basically the VOIP engine used by the openwengo project.