A little while back I mentioned how at Varian Australia the software team has developed a tool that check our code coverage on every commit (each time the build box runs) and fails the build if the coverage falls. Now Nigel is publishing the tool to SourceForge. You can find it here.
This has proven to be very effective. Even with well intentioned TDD it is surprising how easy it is to miss one functional point. As the tool only allows the coverage to go up or stay the same the coverage must, and does, increase with time. It has made a real difference to the team. All code now committed must be 100% tested by unit tests or the fail music will sound within just a few minutes :-).