As of today (Register API for iOS v1.2 and other API's too) we pass a parameter 'callback_url' that is used to return approval data back. But Register blindly passes the returning data with the title of always just 'data'.

Maybe we can pass the API an additional, optional parameter 'callback_datatitle' that defaults to 'data' but we can change it to be maybe 'param' or '$data' or whatever? That way we can better adapt and integrate Square into other Apps and their own url schemes.

(See FileMaker Go problem that expects all callback parameters to be passed under the title 'param')