RxDeadTime_Timestamp.cs

static IObservable<T> DeadTime<T>(this IObservable<T> source, TimeSpan deadTime)
{
    return Observable.Create<T>(o =>
    {
        var subscriptions = new CompositeDisposable();
        var lastTime = DateTimeOffset.MinValue;

        return source
            .Timestamp()    
            .Where(timestamped => timestamped.Timestamp - lastTime > deadTime)
            .Do(timestamped =>
            {
                lastTime = timestamped.Timestamp;
            })
            .Select(timestamped => timestamped.Value)
            .Subscribe(o);
    });
}