The point is an convenience
Unified Communications Server
Java VoIP Softphone (SIP) (replaced by jfPhone)
H.323 Gatekeeper for VoIP and videconferencing
Chat with your friends everywhere, whether you are in space or on eart
Cyber-wrt pbx is embedded system in DD-Wrt router
OpenSource Call Center and Dialer System
TEKSTER is a Computer Application To Send FREE SMS Around the World!
GSM L1-L3 stack with SIP network interfaces