It would automatically remember every page I have visited without requiring an action from me (Doable on desktop browsers). There would be simple browser extension UI that would allow tags, read-later and sharing.
That would probably take no time at all with chrome https://developer.chrome.com/extensions/history - push history events to a synced service, auto-tag content (with something like embedly or alchemy ?) - add some social bells and whistles, sprinkle some flat ui and CSS3 transitions on it - alakazam!
Seems to me that not only did you provide a quick recipe for an implementation, but also provided a name for it!
Shame about the Pokemon, was hoping for something more magical