Is there a good automatic time tracking tool for Mac OS X

I'm searching for an automatic time tracking tool for Mac OS X. I regularly mess up manual time tracking with timers etc., so I want something more automatic: The application should run in background and track more or less everything I do - which applications are active, which sites I browse, how long I'm idle etc. It would then list all the things I do in a timeline and let me specify filters like "Xcode in foreground", "browsing developer.apple.com", etc. Using these filters, I could check how long I worked on what *after* I left work. Is there an application which does this? I'm aware of a website and a client for it, but I'm absolutely NOT comfortable with putting all the things I do on some random website.