Give a try to Osmius.

Fast, scalable and integrates the business view in the tool, as well as a real GIS (you can use it or not), SLA management and BI and datamining views. Everything related to monitoring in made in C++ using the multiplatform near real-time framework ACE, so it's really fast.
The Web console is based on TomCat (J2EE) and you can manage, deploy, configure or update agents from there.
You can develop new events and new agents to monitor "whatever" you want: stock shares, temperatures, web transactions,... it's up to you. And Osmius is real Open: There's no open core, nor closed features, and you can access the documentation, the analysis info, datamodel staff, and (of course) the code.
We are now (I'm in the development team) doing the final tests and dealing with the latest bugs and also testing scalability and the behaviour under stress of receiving millions of events every day, and thousands per seconds. It's working properly.
The D day is July the 30th. Every comment and suggestion, and even hard criticism, is very welcome.
We want Osmius to be:

• Helpful to technical and business staff.
• Easy to understand.
• Robust.

Let's see if we made it.