[Anthem]

WhisperSync is just Amazon's name for their syncing service which basically keeps a record of where you are at in a book on your devices and apps so that you can pick up the book on another device and resume from where you ended on the other.

And I could have sworn that WhisperNet was the cellular component that gave you access to Amazon services over cell networks. Can't remember for sure though. It may refer to something larger than that.