I am implementing the Backendless Push Notification service
https://backendless.com/docs/rest/push_push_notification_setup_androi.html
I have already configured and can register the device to the channel created through the console (Messaging Channels).
For this I have used REST API...
Backendless is pretty popular these days, have a vast amount of features and affordable as well. I wish someone can make a wrapper. I'm ready to donate for that.