Zabbix - Track, record, alert and visualize performance and availability of IT resources
DbNinja - Web-based application for secure and efficient management of MySQL database servers
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.
Adminer - Adminer (formerly phpMinAdmin) is a full-featured database management tool written in PHP.
Prometheus - An open-source systems monitoring and alerting toolkit.
myLittleAdmin - myLittleAdmin is the first web-based management tool specially designed for MS SQL Server.