dart:async should have an easy way to combine multiple streams into one.

Example implementation which supports pause/resume.

Stream merge(List<Stream> streams) {
  int _open = streams.length;
  var c = new StreamController();
  for (var stream in streams) {
    stream.listen(c.add)
         ..onError(c.addError)
         ..onDone(() {
      if (--_open == 0) {
        c.close();
      }
    });
  }
  return c.stream;
}