NCrunch does show this, though I'm not sure how obvious this is in the documentation and its visibility may depend upon your colour scheme.

Basically NCrunch will fade the markers that are covered by any tests for which the results may not be current. You'll notice that as soon as you make a change to the codebase, all the markers will immediately fade out with a partial transparency to show that their results may no longer be current. As soon as all tests that cover a particular line have been executed against the latest version of the source code, the marker will no longer show as partially transparent.

There are other places that NCrunch will also show this information. In the corner spinner, the number in the centre of the spinner will show as faded if it describes information that may be out of date. The Tests Window will also show tests with a question mark icon if their results are not current with the latest version of the codebase, and any text shown in the output window pane on the bottom of the Tests Window will also be a lighter shade of grey.

Sometimes if you are working in a small codebase with very fast running tests, the effect can be difficult to notice because NCrunch is able to execute the tests very quickly. If you think this may apply to you, try adding a Thread.Sleep(5000) into one of your tests so that you can observe how NCrunch handles it.