Another option would be to build a lc-dcc. It's a DCC controller that can easily be built with bluetooth or wifi and has an app for android, apple or windows. You can control trains from your phone, tablet or computer. You can also add potentiometers for manual control of up to 8 assigned engines.If your goal is to have DCC sound but to keep the smartphone control, you would buy a DCC sound locomotive and then add a BlueRailDCC board which would supply the decoder with DCC signals. The 2 amp boards are about 1.5” by .5”.