Is there is a way to send a local message from a Mac to an iOS device *without* the Internet?
If I understand you correctly you're asking how to push local notifications on your Mac to your iOS device (hence using Prowl as an example)? Well since Mavericks/iOS 7 if both your Mac and iOS device support Bluetooth Low Energy, you could use a service based on the Apple Notification  Center Service.
This feature is also covered in this 9to5mac article.