Notification option when specified friend posts content

I had a friend tell me today that he and others (in his opinion) would be more active on the platform if he was able to choose to get a Push notification (or e-mail I suppose) when specific people posted updates or other content to the site. I guess without that little push he just doesn’t thin about it. Is that an option that I just can’t seem to find or something that has been or is being considered? - Thanks