You can only minimally address it from the server side with Notch's current structure. The problem is the entire chunk data is sent to the client, so your machine already knows what is/isn't available in that particular chunk of blocks. Texture packs just omit the common blocks (stone, cobble, etc.) from the chunk stream to allow you to see what's underneath.
It is still monitorable from a server side, as obviously most folks legitimately wouldn't be destroying diamond blocks ever 10 to 20 seconds for hours on end in any normal mining pattern. Not to mention that kind of thing tends to show up in player history, this is all stored in a database after all. Not to mention, it's pretty easy to tell when somebody is mining in complete darkness without skipping a beat.
In summary: Cheats are bad, m'kay ... you shouldn't do it, m'kay.