Some ideas for your synopsis
MobilePay in Android applications
Android wearable (Android API 20W)
Architectures of Android applications: MPC, MVVM, MVC etc.
Kotlin compared to Java (much more that we did in class)
Android (the latest versions), new features
How to make apps for iPhone / comparing iPhone development to Android development
How to make apps for Windows 10 compared to Android
Java for iOS, Windows, etc.
Adapting Android apps to different screen sizes and screen densities.
Android game programming
Android audio, video and camera
Android styles and themes
Android NFC (Near Field Communication) (communication with very nearby devices)
Internationalizing and localizing your Android application to support different languages and cultures.
Dependency injectors for Android, like Dagger
The development enviroment "MIT App Inventor"
Android Broadcast intents and Broadcast receivers
Designing and programming Android apps to run in desktoop browsers
Google Firebase vs
Visual Studio Mobile Center
UI for Xamarin
and many other ideas ...