Since jUnit (and the xUnit family) is just a verification mechanism, it’s a natural fit for service monitoring. This article from JDJ describes using jUnit and JMX to build a service monitoring framework:

This article walks you through the process of setting up a basic service monitor and event handler for a common J2EE n-tier system. Developers of J2EE systems will be able to use JMX4ODP to create testing suites to help them develop more reliable systems. J2EE application administrators will be able to use JMX4ODP to simplify and regulate the management of deployed systems.

Why jUnit?

JUnit bills itself as a regression-testing suite for code objects, but it’s not much of a leap to see it as a tool for distributed system diagnostics. JUnit runs tests by instantiating objects, invoking their methods with known inputs, and checking the output against expected returns.The article is very Java and J2EE focused, but the concepts are applicable to any service monitoring project.