Edit in JSFiddle

var myApp = angular.module('DemoApp', []);

myApp.directive('jnhMustache', [function () {
   var declaration = {};
        
        declaration.restrict = 'E';
        
        declaration.scope = {
            data : '&',
            watch : '='
        };
        
        declaration.transclude = false;
        
        declaration.link = function (scope, element, attrs) {
            function render () {
                var html = Mustache.render(scope.template, scope.data());

                element.html(html);
            };
            
            scope.template = element.html();
            
            element.html('');
            scope.$watch(function () {
                var result = scope.data()[scope.watch].length;
                return result;
            }, function () {
                render();
            }, false);
        };
                                
    return declaration;
}]);

myApp.controller('ExampleController', function ($scope) {
    $scope.myData = {
        name: 'Jon Hartmann',
        friends: [
            'Gowtham',
            'Kiran',
            'Marshall'
        ]
    };
    $scope.watching = 'name';
    
    $scope.addFriend = function () {
        $scope.myData.friends.push('Aundrae');
    };
});

<div ng-app="DemoApp">
    <div ng-controller="ExampleController">
        Name: <input type="text" ng-model="myData.name" /> <br />
        
        <label>
            <input type="radio" ng-model="watching" value="name" /> Name
        </label>
        
        <label>
            <input type="radio" ng-model="watching" value="friends" /> Friends
        </label>
        
        <hr>
        
       Control:
        <pre>{{myData | json}}</pre>
        
        Mustache:
        <jnh-mustache data="myData" watch="watching">
            <div ng-non-bindable>
                <h1>{{name}}</h1>
                
                <ul>
                    {{#friends}}
<li>                    {{.}}</li>
                {{/friends}}
                </ul>
            </div>
        </jnh-mustache>
        
        <button ng-click="addFriend()">Add Friend</button>
    </div>
</div>