We are expecting to find out some more details about Android 4.4 Kit Kat and the Google Nexus 5 later today. Google has now posted some information on its Android Developers Blog, relating to changes to SMS on Android 4.4.
Google has announced that they are providing a fully supported set of APIs for building SMS apps, the new set of APIs is designed to make SMS messaging apps more reliable, and Google are looking to stop developers from using hidden APIs for these apps.
Sending and receiving SMS messages are fundamental features on mobile devices and many developers have built successful apps that enhance this experience on Android. Some of you have built SMS apps using hidden APIs—a practice we discourage because hidden APIs may be changed or removed and new devices are not tested against them for compatibility.
Google are basically looking to remove the use of hidden APIs within SMS applications, and for messaging apps to work with Android 4.4 Kit Kat they will need to use the new set of APIs that Google has provided.
The news was posted on the Android Developers Blog yesterday, which is interesting timing, considering that we are expecting the Google Nexus 5 with Android 4.4 Kit Kat to be made official later today.
Source Android Developers Blog