earlier i have done something vaguely similar - using Perl
what i have done:
keep checking a particular directory for presence of files (this was a cron job running, say every few hour)
if files are found, check if they satisfy the criteria - based on filename
if the file satisfies the criteria, do something with it, then move it to
archive directory, and send an e-mail to the concerned people
if the file fails to satify the criteria, move it to
failed directory and send an e-mail to the concerned people
If you are planning to use Perl, module
MIME::Lite is good for sending detailed e-mails (supports attachments). If you are looking for basic e-mail functionality, try module
Mail::Send
if you don't want to run your program as a cron job, then another option is to make a daemon