Android
Android code is based on the rosjava client and core libraries and has been recently upgraded to work seamlessly with android studio and the new google supported android gradle plugins.
Official source code for android projects can be found on github in the rosjava organisation.
MATLAB
Package for run ROS inside Matlab
Documentation
Android development is supported via Damon's rosjava implementation.
Overview : been some large jumps made in the last few months, details here.
Official Packages : list of all official and semi-official packages in the rosjava-android ecosystem.
Android Studio : using the new studio to compile, hack and deploy your projects.
FAQ : frequently asked questions.