This free Android application connects to a WiThrottle Server. Supported servers include JMRI, DCC-EX, MRC Prodigy WiFi, Digitrax LnWi, WifiTrax (for NCE) and IoTT Stick. 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].For older devices, you can try older versions of EngineDriver from the [Downloads] page.