Install http://play.google.com/store/apps/details?id=com.msdroid - see also http://www.msdroid.com/
Then you need to save this file: https://svn.code.sf.net/p/rusefi/code/trunk/firmware/tunerstudio/rusefi.ini on your Android device.
Move the rusefi.ini file you've just downloaded to MSDroid/ini folder (I've used https://play.google.com/store/apps/details?id=com.estrongs.android.pop for that)
In order to connect msDroid to rusEFI you would need to tap 'App settings' and select the paired Bluetooth device. As of today, msDroid does not turn Bluetooth on automatically.