MonSpark

Have purchased highest Tier (1000 Monitors) months ago to get all future monitor solutions under development. This was a good idea, because the tool grows about every 10 days by small or big improvements ... and completely new functions. There is a well documented changelog (see roadmap) and tips within the backend to be able to test out new capabilities in a timely manner as well.

The scope goes far beyond the usual uptime monitor, and some things require a bit of testing to understand how to use them in a meaningful way. But learning effort is a good thing - shows that the developers have thought about different usage scenarios and are trying to implement them.

If the tool ever returns to Appsumo, it is definitely a recommended purchase.