If you're looking for a ready-to-use solution, I don't think you're going to have much luck at this moment in time.
If you're willing to get your hands dirty and write some code, I would suggest looking at Pushbullet and its API. It's very easy to get started with and it can send push notifications to smartphones, web browsers and desktops (as long as they're running the requisite app or extension).
You could incorporate something as simple as this into a custom module:
$title = 'Some title text';
$body = 'Some body text';
$client = \Drupal::httpClient();
$request = $client->post('https://api.pushbullet.com/v2/pushes', array(
'headers' => array(
'Access-Token' => 'your_access_token_here',
'json' => array(
'type' => 'note',
'title' => $title,
'body' => $body,
You're not limited to simple text notifications either; it can push links and files as well.