ObservableContainer

IObservableContainerItem.cs

public interface IObservableContainerItem<T>
{
    T Observed { get; set; }
}

ObservableContainer.cs

using System.Collections.ObjectModel;
using System.Linq;

public class ObservableContainer<O, U> : ObservableCollection<O> where O : IObservableContainerItem<U>, new()
{
    public ObservableCollection<U> UnderObservation { get; private set; }

    public ObservableContainer(ObservableCollection<U> underObservation)
        : base(underObservation.Select(u => NewObserver(u)))
    {
        UnderObservation = underObservation;
        UnderObservation.CollectionChanged += UnderObservation_CollectionChanged;
    }

    private void UnderObservation_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        if (e.NewItems != null)
        {
            foreach (var item in e.NewItems.OfType<U>())
            {
                Add(NewObserver(item));
            }
        }
        if (e.OldItems != null)
        {
            foreach (var item in e.OldItems.OfType<U>())
            {
                Remove(this.First(o => ((IObservableContainerItem<U>)o).Observed.Equals(item)));
            }
        }
    }

    private static O NewObserver(U u)
    {
        var observer = new O();
        ((IObservableContainerItem<U>)observer).Observed = u;
        return observer;
    }
}