Indeed, it's called Plasma Search, available in system settings. Providers can be enabled, disabled, and configured at will. I can't imagine it would be all that difficult to code your own and get it hooked up in there, if you were so inclined. Personally I just unchecked everything except "Applications" and I use it like a quick launcher. Works great for my purposes.

I use it exactly like that too. It's too jarring to get anything else in the results for me and while I can't imagine why anyone would include any other source, to each their own.