TeamViewer - TeamViewer lets you establish a connection to any PC or server within just a few seconds.
Asterisk - An open source telephony switching and private branch exchange service for Linux.
ConnectWise Control - ConnectWise Control is a mobile app that allows you to instantly connect with another system from anywhere with a connection to the internet. The software not only comes in a mobile app, but it has a desktop version as well for complete coverage.
FreeSWITCH - FreeSWITCH is an open-source media application designed to support popular protools such as SIP and WebRTC and provides a platform to develop voice and video applications.
VNC Connect - VNC is remote access and control software which allows you to view and fully interact with one...
freepbx - FreePBX is a web-based open source GUI that controls and manages Asterisk (PBX).