This free Android application connects to a WiThrottle Server. Supported servers include JMRI, DCC-EX, MRC Prodigy WiFi, Digitrax LnWi, and WifiTrax (for NCE). Once connected, you can control your locomotives and your entire model railroad. Speed, direction, and up to 29 DCC functions are supported for one to six locomotives or consists. You can create and edit consists (software-defined). You can also control layout power, turnouts, routes, and access JMRI web panels and windows.
EngineDriver is open source software. The source code is available on GitHub [HERE].
EngineDriver currently has minSDKVersion set to 16, which equates to Android OS 4.1 (JELLYBEAN). Info on minSDKVersion available [here].