No-IP - Dynamic DNS and Managed DNS Provider
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Duck DNS - Free dynamic DNS hosted on Amazon VPC
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.
FreeDNS by Afraid.org - Free DNS hosting, lets you fully manage your own domain. Dynamic DNS and Static DNS services available. You may also create hosts off other domains that we host upon the domain owners consent, we have several domains to choose from!
Nagios - Complete monitoring and alerting for servers, switches, applications, and services