Using GCM for iOS means sending different fields to GCM than when sending notifications to Android devices. With the Unified Interface you don't have to think about this.
The Unified Interface provides a simple interface for sending notifications, taking away most of the hassle.
Spike0 (first prototype) of the API is live at unified-interface-spike0.notif.deranged.dk:3098 and you can read the documentation on Github.
To get started, register your app with its API key and app-type ("iOS" or "Android").
For example:
curl -vkX POST http://unified-interface-spike0.notif.deranged.dk:3098/app \
--header 'Content-Type: application/json' \
--data '{ "apiKey": "yourApiKey", "appType": "Android" }'
This returns an appToken, which you will use to send notifications.
(Note that you have to replace the apiKey above with your actual API key for the appToken to work.)
You need a registration ID for the app to send a notification.
Here is an example of a data notification:
curl -vkX POST http://unified-interface-spike0.notif.deranged.dk:3098/data-notification \
--header 'Content-Type: application/json' \
--header 'App-Token: YouAppTokenFromBefore' \
--data '{ "to": "registrationIdOfYourAppOnTargetDevice",\
"type": "test-notification",\
"collapse": false,\
"data": {"foo": "bar"}}'
The Unified Interface is hosted for free prior to real release. Try it, and remember to pop by the Github page if you have any issues.