shouldn't be difficult to do. just open a connection to the desired server and store the file in a string (see: http://www.php.net/manual/en/function.fopen.php).
then you create a md5 hash out of this string and insert hash and file-string into your DB.
when you get the file the next time you just compare the current md5 hash with the hash in your DB. if it's different, then you update the file stored in your DB and send the e-mail to the specified receivers.
i guess you should run the script once per day. a cronjob would be the best way to do this...
