A professionally built external sensor box eGyro-BT mounted at a proper place (e.g. the floor of an aircraft ) sends attitude data via bluetooth to this app that displays the artificial horizon and allows the user to set up communication and dynamic parameters.
This app is free, however for use in flight, an eGyro-BT sensor box must be purchased. Without the eGyro-BT sensors it will work only in demo mode. Demo mode is not suitable for flying.
More info to be found here: http://andromedar.ch/english/products/artificial_horizon/index.html