My team uses AlertSite for multiple types of monitoring requirements. The main purpose of the tool is synthetic monitoring where you navigate to the website login, find some patterns, then save the searches.
AlertSite also has a feature called Deja-Click where you can create a recording and configure it to the website, and based on the timeframe, it executes each recording every time, so in case there are some changes in the UI, it gets stuck and it will notify you.
AlertSite is also being used for URL checks, TCP connections, API monitoring, HTTP monitoring, etc., depending on internal applications.
AlertSite benefits our company because we have configured or integrated it with PagerDuty for the alerts, especially because there are specific critical applications we need to check every minute or two, based on our requirements. These critical alerts are configured on AlertSite via PagerDuty, then connected to ServiceNow, so whenever there are issues, alerts are triggered very quickly. Everyone in our team uses AlertSite, and anyone on call finds the tool very useful.