I have been using an Air Keyboard app Air Keyboard appon my ipad to use as a touch screen ticket machine.
I used the textures from the SD200 texture folder for the keypad and also the money change buttons and edited them together so that I can give tickets, give change and take money all by the press of the buttons on the ipad.
Not wanting to stop at that have now got an old Wayfarer 3 ticket machine and will connect that to OMSI via a arduino board, I will most probably then use air keyboard to do a dashboard layout for the light switches etc(as have not got the room for real dashboard).
Just waiting for the next Omsi 2 patch that is due any day now.
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Jason