DeskAlerts - Send alerts to any corporate device: PCs, phones, tablets, etc.
PagerDuty - Cloud based monitoring service
Notifuse - A 1-to-many notification API that's simple to use
VictorOps - We make on-call suck less & help teams to solve problems faster.
Text Alerts - Mobile Text Alerts allows administrators to send out mass SMS text messages to groups, it is useful way to keep group members informed about quick announcements.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.