I've posted a plug-in action that allows you to send notifications to the Pushover service. Notifications can be sent to iOS, Android or desktop computers.
I've posted the plug-in, along with instructions on my git hub page:
Pushover Plug-in on GitHub
The Pushover service is free and you'll need to create an application API key to use the Pushover plug-in. Pushover allows 7,500 notifications/month per user for free so unless you're sending a lot of notifications it should remain free for you.