Listener.js

// Element Listener Mixin
(function(){

var property = '$listener';
var setup = function(element){
	var listener = new Events, removeEvent = listener.removeEvent;
	listener.removeEvent = function(key, value){
		removeEvent.call(this, key, value);
		element.removeEvent(key, value);
	};
	return listener;
};

this.Listener = new Class({

	attach: function(key, value){
		if (!this[property]) this[property] = setup(this.toElement());
		this[property].addEvent(key, value);
		this.toElement().addEvent(key, value);
	}.overloadSetter(),

	detach: function(key, value){
		if (this[property]){
			if (typeof key == 'string') this[property].removeEvent(key, value);
			else this[property].removeEvents(key);	
		}
		return this;
	},

	toElement: function(){
		return this.element;
	}

});

}).call(this);

// Implementation
var MyClass = new Class({
	
	Implements: [Listener, Class.Binds],
	
	initialize: function(){
		this.element = new Element('div');
		
		this.attach({
			click: this.bound('onClick'),
			'keyup:relay(:input)': this.bound('onKeyUp')
		});
	}
	
});

// Use
var myInstance = new MyClass();
myInstance.detach();