The thought of tapping my LCD hard enough for a sound to be picked up over the ambient sounds in my room makes my skin crawl. NOTHING touches my LCDs.
The feature set for v1 is set. We've done all of the "Mac first" features we have time for. Everything goes into the hopper for v1.0+, so be assured that it will be evaluated. I've not messed with the sound input before so I don't really know what is involved with trying to discriminate a tapping sound from the phone ringing, etc.
Keep the ideas coming. Even if they don't make it in right away we enjoy hearing other people's ideas, and if they don't go in as you imagine them they still may spark other ideas which do.