I am interested to trigger a certain action upon receiving an email from specific address with specific subject. In order to be able to do so I need to implement monitorin
People seem to be pumped up about Lamson:
https://github.com/zedshaw/lamson
It's an SMTP server written entirely in Python. I'm sure you could leverage that to do everything you need - just forward the gmail messages to that SMTP server and then do what you will.
However, I think it's probably easiest to do the ATOM feed recommendation above.
EDIT: Lamson has been abandoned