a quick and simple implementation of Pausable

program.cs

static void Main(string[] args)
{
    var range = Observable.Interval(TimeSpan.FromSeconds(1));

    var sampler = new Subject<bool>();

    var sendWhileTrue = range.CombineLatest(sampler, Tuple.Create)
        .Where(tuple => tuple.Item2)
        .Select(tuple => tuple.Item1)
        .DistinctUntilChanged();
            
    var subscription = sendWhileTrue.Subscribe(
        next => Console.WriteLine("Got value: " + next),
        ex => Console.WriteLine("Got error: " + ex),
        () => Console.WriteLine("Completed"));

    string key;

    do
    {
        key = Console.ReadLine();
        if (key == null) break;

        if (key.Equals("S", StringComparison.OrdinalIgnoreCase))
        {
            sampler.OnNext(true);
        }

        if (key.Equals("X", StringComparison.OrdinalIgnoreCase))
        {
            sampler.OnNext(false);
        }

    } while (!key.Equals("Q", StringComparison.OrdinalIgnoreCase));

    subscription.Dispose();

    Console.ReadKey();
}