There's a dozen services that provide hosted version control, hosted ticket tracking, hosted project management, and combinations of all of the above, there's even hosted web-based IDEs. But nobody's yet offered a hosted continuous integration service; at least that I can find. The concept seems simple enough: I register and provide the URL to my source code repository, it grabs my code and builds it via ant/rake/whatever, then runs the suite of tests and some metrics (code coverage, performance, etc.). Is there some prohibitive barrier to entry I'm not considering?