It's simple. No other operating systems offer the openness, flexibility, interactivity and user experience that Android & Linux do. Android is not limited to phones and tablets, it is making inroads into industrial and embedded systems too. Linux has been the mainstay of critical systems for a long time.
Kernel and Device Drivers
Android & Linux build for boards, devices
Custom kernels and BSP
Device drivers customization
Boot-time optimization
Power management
Android & Linux Customization
Custom libraries and integration
OpenGL, AV streaming, AV acceleration
Integration of new peripherals
Custom launcher, themes, widgets
Security and authentication
Android and Linux Applications
Real-time, camera, VoIP apps
Native apps using NDK
Sensors, NFC, Augmented Reality
UI/UX design
Porting apps from Linux, iOS