Marat Fayzullin has ported his (commercial) MasterSystem, GameGear, SG-1000, SC-3000 and SF-7000 emulator MasterGear to the Android platform: MasterGear for Android

* Added a proper transparent virtual joystick in the landscape mode. See "Settings" to configure or go back to the old joystick.
* Made tactile feedback strength configurable.
* Added button assignments for diagonal directions.
* Added persistent fast-forwarding option.
* Added low disk space warning.
* Made user-assigned key mappings override default key mappings.
* Xperia Play [X] button now acts as FIRE-A (was START before).