What are some alternatives?
PagerDuty - Cloud based monitoring service
LogicMonitor - LogicMonitor is the SaaS performance monitoring platform for the world's best IT teams. Deploy Fast, Monitor More, Improve Ops.
Squadcast - Intelligent IT Incident Management & Alerting and monitoring software for Cloud based applications
Zabbix - Track, record, alert and visualize performance and availability of IT resources
OpsGenie - Alerting and On-Call Management for Dev&Ops Teams
Site24x7 - Site24x7 offers both free & paid website monitoring services. Monitor websites remotely and receive instant email/sms alerts if your website becomes unavailable. View uptime & performance graphs of your website monitors.