Coe Coverage as a service would be cool, but you need to run the tests to generate it. That means you can get it as a build artifact in some CI systems, but you'll still need the gem setup.

I like that the code coverage is always running. I look at it after any refactoring that causes big test changes, to make sure that I didn't introduce gaps in coverage. I'd also like to have the build fail if the coverage drops; we have a Trello research card for that, but I haven't tried it out yet.