https://github.com/Komodo/KomodoEdit/wiki/138-events-and-notifications
var obsSvc = Components.classes['@mozilla.org/observer-service;1'].getService(Components.interfaces.nsIObserverService);
var listener = {
observe: function(subject, topic, data) {
alert("received observer subject: " + subject);
}
};
obsSvc.addObserver(listener, "application-activated", false);
var obsSvc = Components.classes['@mozilla.org/observer-service;1'].getService(Components.interfaces.nsIObserverService);
obsSvc.notifyObservers(null, "my-topic", "some string data");