Zenity - Zenity is a tool that allows you to display GTK dialog boxes in commandline and shell scripts.
ShoutOUT - All in one business texting tool to send personalized alerts, promotions, reminders, short links and marketing campaigns, for any SMEs (hotels, restaurants, education, non profits, Woocommerce, banks, healthcare, agencies, supermarkets, weddings)
Yad - Yad (yet another dialog) is a fork of Zenity with many improvements, such as custom buttons...
Trumpia - SMS Marketing and Marketing Automation software for Mass SMS, internal communications & emergency alerts. #1 Text Messaging Service used by Fortune 500s.
VisualWX - Visualwx aims to be the ultimate RAD tool, designed for c++, python, perl, ruby, lua and wxWidgets.
Clickatell - Simple, reliable mobile messaging cloud.