Improved systems and methods for establishing peer-to-peer calls such as voice over IP calls and video over IP calls. In various embodiments of the invention, SMTP messages are exchanged between devices using a SMTP server, with the SMTP messages including IP address information. With this arrangement, the need for SIP service providers can be eliminated. In other embodiments of the present invention, SMS messages including IP address information are transmitted between devices during a GSM or other type of telephone call, enabling the call to “migrate” to a VoIP or video over IP call.