One Call Now - One Call Now's message notification delivers automated phone calls, SMS text messages and emails within moments to any group.
RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Notifuse - A 1-to-many notification API that's simple to use
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
OnPage - OnPage critical alert and incident management system enables rapid resolution of critical IT, healthcare or IoT incidents through efficient communication.
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs