I had to disable the plugin because it became the #1 resource hog on my mediatemple grid hosting account. From the MediaTemple GPU reports:
Method [?] Path [?] HTTP response [?] Hits [?] IORead [?] IOWrite [?] GPUs / hit [?] %of total [?] GPUs [?] GET <my site>/wp-content/plugins/wordpress-file-monitor/wordpress-file-monitor.php 200 5188 1900864 365296 0.0142 9.16% 73.4415
It means that 10% of all GPU on the account was absorbed by this plugin, to make it worse, I had it activated in multiple blogs, all summing up:
GET <another_blog>/wp-content/plugins/wordpress-file-monitor/wordpress-file-monitor.php 500 93 37968496 0 0.2267 2.63% 21.0849
So I really like this Idea but maybe another solution is needed. I think I might have to resort to writing a perl script to do the same or resort to http://sourceforge.net/projects/tripwire/ but that looks daunting to install.