Please take a look at the iOS push payload at https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/TheNotificationPayload.html#//apple_ref/doc/uid/TP40008194-CH107-SW1
"category" is not supported in iOSAps when push.sendPayload(user,iOSAps, iOSExtras, androidPayload, callback).
At present we do not have this capability, but I will turn this into a feature request and get back to you when I know more information.
Sounds great. Thanks.
The Kinvey Engineering has reviewed this enhancement request and has decided to include it as part of a number of Push Usability Improvements that Kinvey intends to development that will be available in the Q3/Q4 timeframe of 2016 (last half of this year) so it is now included in our Product Roadmap.
Please let us know if you have additional questions.