The light client reference wallet has been built! Sapling shielded transactions now work on mobile devices and we are ready for third-party devs to start providing feedback on the code. What previously required gigabytes of data on a server is now accomplished with megabytes of data and computation suitable for a phone.
To get started, we recommend looking at our Android SDK, which interacts with the server (lightwalletd) and light client (librustzcash). These resources provide an overview of how all the parts work together— for instance, see what the light client requests from the server, how the received inputs are processed, and how those outputs are used to create transactions.