I tend to type really quick and jumble words at times, would be pretty nice to have....perhaps through an extension or something?
If you're on OS X 10.7 Lion or 10.8 Mountain Lion there is spell checking available. It's not universal since some applications don't use a standard text box.
Mountain Lion has iOS like spell check APIs, it is up to the developer if they implement it in their application. It is supported in Mail and Safari though - which can be rather annoying at times, it autocorrects names and terminology. I have already sent out some rather weird emails
How is it enabled I'll give it a shot. I looked in System settings and keyboard and didn't see anything.