I took the lazy way out and just wrote a script to scrape El Presidente's masterpaystatus.txt and output it to a monitoring friendly format every 10 minutes.
If you point
Uptime Robot to monitor the URL:
http://edrake.net/drk/mnpaystatus.txt
And alert when "Keyword Not Exists" for your MN address followed by a ":-":
XaiLY9M9PjhYg26jzxuMhLxKkMdeZuG9yv:-
With "Monitoring Interval" every 5 minutes, it should alert you whenever you get a payment, then reset automatically after the next check or two.
When it detects a new payment, my script will change your address line to show number of payments instead of "-", but will then revert to "-" after the next poll. This basically means that you don't have to log into Uptime Robot and edit your "Keyword Not Exists" field every time you get a payment.
It seems to work for me, but I've only tested it on a couple payments, so let me know if you have any feedback!