With ngModelOptions in Angular 1.3 you can turn your model into a getter/setter function to have greater control over your model.
In order to use getterSetter I found myself using arguments.length to allow users to clear values. I've also got updateOn: 'blur' in my model options in my use case.
vm.inputValue = function(val) {
return arguments.length ? (_val = val) : _val;
}