[CentOS] reinventing the wheel? page checker

Not sure if there is an app like this yet.
I want to keep tabs on my web applications and thought of using a 'page 
checker'/

I was thinking either running a sum on the directory or each file...but 
thinking a simple date check would
be fine.

The idea is web application, except the uploads area for photos, never 
has changes to its files except when I change it.

However, if it gets injected or hacked, I would want to know right away.

So thinking of running a script every minute looking for files where the 
date changed since 'x' date or something like that.

Anything out there like that?

thanks