DeskAlerts - Send alerts to any corporate device: PCs, phones, tablets, etc.
One Call Now - One Call Now's message notification delivers automated phone calls, SMS text messages and emails within moments to any group.
DERDACK SIGNL4 - DERDACK SIGNL4 is a simple yet powerful plug and play cloud-based mobile alert solution that allows you to send alerts via app, text, and voice.
OnPage - OnPage critical alert and incident management system enables rapid resolution of critical IT, healthcare or IoT incidents through efficient communication.
Notifuse - A 1-to-many notification API that's simple to use
Metric.live - Real-time and advanced periodic alerts for Google Analytics.