I'm not sure if you've had to chance to look at it yet, but we have an API that does just that!
The Push API allows you to be able to send a standard JSON structure that can target either your iOS or Android device, or both at the same time if you want.
In addition to that, any iOS and Android specific features you want to include in your push, you can specify the fields in their respective payload structure to include such things as sound, badges, pictures, etc.
I would definitely recommend taking a look at that JSON structure. Also, you may find our Example API Requests documentation helpful as well as you're putting together your requests.