Try looking at changetrack and tripwire. These are both fairly widely used programs for doing some or all of what you're after. Changetrack, I believe, mainly handles content changes (emailing diffs to root, etc), while tripwire can handle *all kinds* of stuff, like mod times, perms, size, etc., along with a dizzying array of options for things like "growable" files (e.g., only alert me if this log file should *decrease* in size), etc.
Tripwire is available in Free and commercial versions, and the Free one is supported as many free things. However, if you were going to roll your own anyhow, dealing with the already-thought-out complexity of tripwire might be a blessing.