Edit in JSFiddle

<div ng-app='app'>
    <div>
        <input type='text' placeholder='Haz clic aquí' focusable />
    </div>
</div

angular.module('app', [])
    .directive('focusable', function() {
        return {
            compile: function(element, attrs) {
                element.bind('focus', function() {
                    element.addClass('focused');  
                    element.attr('placeholder', 'Haz clic fuera de aquí')
                });
                element.bind('blur', function() {
                    element.removeClass('focused');  
                    element.attr('placeholder', 'Haz clic aquí')
                });
            }
        }
    });

.focused {
    background-color: green;
}