Atlassian has released Clover 2.1, a $1200 payware test coverage tool.
Clover modifies the source code to enable it to follow which statements are executed when, and keeps a running count of how many times each statement is executed during the test suite. Any statement that executes zero times is not being tested.
I use Clover with Ant, but there's also an Eclipse plug-in.
Clover can generate test coverage reports in
XML, HTML, PDF, or via a Swing Viewer.
Version 2.1 "allows users to tailor code coverage reporting even more closely to their needs. Configurable risk metrics let you choose an algorithm that matches your definition of a project risk. 'Coverage Clouds' are now available for every individual package. Building on the per-test coverage that was introduced in Clover 2.0, in Clover 2.1 reports from merged databases now include per-test coverage data."