How to get push notification when a file in google drive changes using google api

Are there any ways of getting file changes pushed to your website if a user signed up with google drive? For my site, I am doing some post processing on google documents, and it would be nice if i can get user to identify files they would like to track and every time they change the file, I will automatically get a notification and I can download the new version on my end. I tried searching around on google drive api page, and i can only find "realtime api" which seem to be an api to sync changes between two of my own files, and not push changes to me from google drive. Thanks a lot!