Edit in JSFiddle

<p><input type="text" id="text1"></input></p>
<p>The text input value is: <label id="label1"></label></p>
<p>The text input value is: <label id="label2"></label></p>
<p><input type=button id="button1" value="Send"/></p>

var myTextInput = {};
myTextInput.subscribers = [];
myTextInput.subscribe = function(action) { this.subscribers.push(action); };
myTextInput.id = 'input#text1';
myTextInput.activate = function() {
   jQuery(this.id).keyup(function() {
       for (var i=0; i<this.subscribers.length; i++) {
           this.subscribers[i](jQuery(this.id).val());
       }
   });
   jQuery(this.id).trigger('keyup');
};    

myTextInput.subscribe(function(value) { jQuery('label#label1').text(value); });
myTextInput.subscribe(function(value) { jQuery('label#label2').text(value !== '' ? 'correct' : 'incorrect'); });
myTextInput.subscribe(function(value) { if (value === '') jQuery('input#button1').attr('disabled', 'disabled'); else jQuery('input#button1').removeAttr('disabled'); });
myTextInput.activate();