Are you suggesting sending a notification every time a watched user posts? I think it would be unmanageable with the post counts.
Btw there is a RSS feed of each user. I think it can provide exactly what you are looking for. With RSS reader of your choice you can even track multiple users. Just google RSS reader or select one in your app store. There are browser extensions or stand-alone apps.
Add this URL to your RSS reader: https://overgrow.com/u/G-paS/activity.rss
Just replace a username in the URL above.