RepeatAfterDelay.cs

IObservable<T> RepeatAfterDelay<T>(this IObservable<T> source, TimeSpan delay, IScheduler scheduler)
{
    var delay = Observable.Empty<T>().Delay(delay, scheduler);

    return Observable.Concat(source, delay).Repeat();
}

https://github.com/bman654

Observable<Unit> AsObservable(this CancellationToken token)
{
    return Observable.Create<Unit>(observer =>
    {
        return token.Register(() =>
        {
            observer.OnNext(Unit.Default);
            observer.OnCompleted();
        });
    });
}