I use Arduinos as a cheap way of interfacing to Loconet for control of my layout. I have cards for reporting the status of an object on the layout and cards for controling objects on the layout :-

• Lighting,

• switch / point motors,

• signals

• scripted events.

In the future I want to explore using the Arduino to have sound events on the layout as well. The arduino has the ability to play recorded MP3 sound tracks. I want to use this for things like the sounds of a factory or a platform, basically I will use PIR sesnors to detect a person is in a certain space and play the apropriate sound file for that space.