Edit in JSFiddle

function BondController($scope) {
    $scope.name = 'Kalle';
    $scope.$watch('name', function(newValue, oldValue){
       if(newValue == 'James Bond'){
           alert('I\'ve been expecting you, mr. Bond');
       }
   });
}

<div ng-app>
    <div ng-controller="BondController">
      <h1>My name is {{name}}</h1>
      <input type="text" ng-model="name">
    </div>
</div>