Hipsip is Session Initiation Protocol (SIP) service for mobile phone users worldwide. Hipsip combines SIP and Skype calling. The service is accessible from both regular and SIP enabled mobile phones, and Hipsip makes voice-over-internet calls possible from any mobile web browser. Users should download the Hipsip Bridge application and install it on their home computer to use the service. Then users need to access Hipsip from their mobile phone to call any Skype or SIP user for the cost of a local phone call.