When you're not looking at a page, a realtime notification in the bottom left corner isn't very useful. However, most (modern) browsers already implement the soon-to-be-standard [[ http://www.w3.org/TR/notifications/ | Web Notifications ]].
It shouldn't be too hard to implement (I already hacked it into `rsrc/js/core/Notification.js`). This also seems like a good opportunity to contribute something back but I would love some feedback as to how to approach it "correctly".