Chances are, you never heard about Xymon (formely Hobbit), so let me give you some idea. It's actually pretty decent monitoring system - if you still live in 90s. :D But hey, let's give credit where it's due, compared to other systems at that time, it was reasonably fast, has quite easy to understand configuration, comes with many standard checks out of the box and comes with a web interface. Probably that's why some people still use it to this day.
In our company it's one of those legacy systems, that we need to replace, so as a first step, let's see if we can get some of the data out while we're still using it.