PagerDuty - Cloud based monitoring service
logstash - logstash is a tool for managing events and logs.
VictorOps - We make on-call suck less & help teams to solve problems faster.
rsyslog - Rsyslog is an enhanced syslogd supporting, among others, MySQL, PostgreSQL, failover log...
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.
Graylog - Graylog is an open source log management platform for collecting, indexing, and analyzing both structured and unstructured data.