I am looking to a RSS feed reader or system for Mac OS X that checks every minute or so the feed, and when there are changes it sends me instantly an email. Do you know about something similar?
rss2email is an awesome script for this purpose (it can even parse Atom feeds). It is officially supported on Linux and Windows, but as it is a Python script, it should work on OS X just fine, as Python is installed by default on it.
To check the feeds every minute you can add an entry like this to