Uptime monitoring
Per-site checks with configurable interval, expected status, string match, timeout, and failure thresholds. Incident history kept for every site.
Set the check interval, the expected status code, an optional string match for "is the homepage actually serving the right content", a timeout, and the consecutive-failure threshold before an alert fires. Incidents are kept per site with timestamps, so the "was it down at 03:14?" question gets answered without digging through logs.