Edit in JSFiddle

var HelloCtrl = function($scope) {
    $scope.$watch(function () {
        return Math.random();
    });
};

<div ng-app ng-controller="HelloCtrl">
    <label>Name:</label>
    <input type="text" ng-model="yourName" placeholder="Enter a name here" />
    <hr/>
    <h1>Hello {{yourName}}!</h1>
</div>