"Virtual" slugs?

[mvlcek]

Just thinking aloud here: Couldn't you use a check with return_page_slug(), sort of like this:

Within the filter you can do this (it's equivalent to checking the global $id variable), as it is always called from the frontend. Outside you would have to test first, if it is the frontend, e.g. if (function_exists('return_page_slug')) ...