InitIn your directive you could bind your attribute with ngModel :
app.directive('myDirective', function() {
return {
restrict: 'AE',
scope: {
myModel: '=ngModel'
},
template:'<input ng-model="myModel"/>'
}});
You should be able to use is from your HTML like this :
<my-directive ng-model="whatyouwant"></my-directive>
An example : http://jsfiddle.net/maxdow/6GU6x/