PagerDuty - Cloud based monitoring service
One Call Now - One Call Now's message notification delivers automated phone calls, SMS text messages and emails within moments to any group.
OpsGenie - Alerting and On-Call Management for Dev&Ops Teams
Squadcast - Automate incident response, reduce downtime and enhance your tech teams’ delivery with a unified platform.
xMatters - xMatters transforms event data into intelligent communication IT teams, avoiding outages and disruptions
Notifuse - A 1-to-many notification API that's simple to use