This is a library for Seedvault storage backup. It can also be used by other apps wanting to provide storage backup feature.
Please see the design document for more information.
There is also a demo app that illustrates the working of the library and does not need to be a system app with elevated permissions. It can be built and installed as a regular app requesting permissions at runtime.
The design document mentions several limitations of this initial implementation. One of them is that you cannot backup more than one device to the same storage location.