If the point of your question is that you are starting with anonymous objects,
then wrapping each item with a mx.utils.ObjectProxy will do what you want by
making each property of the proxied object bindable.
The other alternative is not to use an anonymous object, but to create a
concrete class for the tasks:
class Task {
[Bindable] public var label:String;
}
Ultimately this way is better for several reasons. (Note that as shown the mxml
compiler will have to rewrite the class to implement IEventDispatcher)