I have the channel working for sending notifications of mentions via Pushover [pushover.net], I just don't a front end settings portal yet. That will likely be this weekend judging by my schedule the next few days.
If anyone would like me to plug them into the back-end in the meantime I'd be more than happy to do that. Just hit me up with an ADN PM (@thrrgilag), XMPP ([email protected]), or Telegram (https://telegram.me/thrrgilag).
Oh and if there are other notification channels/services folks would like to see just let me know and I might add that too if it's not too complicated. :-)