AngularJS Selection - setting ng-model in controller does not update selected value

I'm facing a problem in upgrading my ng-model in selection.
I have the following HTML:

<div ng-app>
    <div ng-controller="Ctrl">
        <select ng-model="viewmodel.inputDevice"
        ng-options="i.label for i in viewmodel.inputDevices">
        </select>
    </div>
</div>

And the following code:

function Ctrl($scope) {
     // view model
    $scope.viewmodel = new function () {
        var self = this;
        var elem1 = {
            value: '1',
            label: 'input1'
        };

        var elem2 = {
            value: '2',
            label: 'input2'
        }

        self.inputDevices = [elem1, elem2];

        self.inputDevice = {
            value: '1',
            label: 'input1'
        };
    };
}  

You can use the following JSFiddle

What I want to do is put in inputDevice the same values that the first device has in the collection inputDevices.
I know that I can pass elem1 and it will work however i can't do it since i want to save the selection in Local Storage and than restore it to the ng-model object.
Any suggestion will be grateful
Thanks