Monitoring folder activity

[Chad Albert]

I am in need of a way to trigger an action when a file is written to
user's home directories.  I am sure there is a way to do this, but I
don't know where to look.  What I want to do is allow users to sftp a
file into their home directory, then once the file is written, I want a
server side process to email or otherwise transfer the file to another
location so that it can be processed with some third party tools by a
Windows user.  Can anyone help me out?