Zenity - Zenity is a tool that allows you to display GTK dialog boxes in commandline and shell scripts.
RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Yad - Yad (yet another dialog) is a fork of Zenity with many improvements, such as custom buttons...
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
Glade - Glade is a RAD tool to enable quick & easy development of user interfaces for the GTK+ toolkit...
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs