There is a lot of prep steps involved in packaging the app and metadata properly, but once that done the submission to the respective store is pretty straight-forward and simple for either.
Apple Store is easiest to do automated using a simple CLI call to 'altool' using the Application Loader.
$ altool --validate-app -f file -u username [-p password] [--output-format xml]
$ altool --upload-app -f file -u username [-p password] [--output-format xml]
Of course, there is more to testing, approval, release process and account mgmt based on the content, etc, which Google covers here:
http://developer.android.com/distribute/googleplay/developer-console.html
You could also consider using TestFairy with their Upload API.
I'd like to see someone in the community use the RDK and assemble a pack using the TestFairy REST API.