title: Track the (number of) observers in an Observable?
body: <p>I have an observable which represents a stream of stock prices. If there are no observers on my observable sequence I'd like to be able to disconnect from the remote server that is supplying the stream of prices, but I don't want to do that until every observer has called Dispose(). Then in a similar fashion, when the first person calls Subscribe I'd like to reconnect to the remote server.</p>
  
  <p>Is there a way to figure out how many observers have called subscribe on an observable? Or perhaps a way to know when observers are calling Subscribe or Dispose? </p>