Art & Technology student Tiuri de Jong did a project on Arduino and Unity communication. The goal was (and still is) to create an easy workflow and tutorial on how to connect Arduino with Unity (free version). Due the serial implementation in the Mac OSX version of Unity, this part still doesn’t work. Suggestions and contributions are welcome on the project page.
Project: unity-arduino with serial connection
The link is established in Windows using the Mono implementation of System.IO.Ports.
For Mac/OSX users, I’ve made an implementation that uses SerialProxy because direct serial connection doesn’t work on the mac. The problem is, though, that the SerialProxy implementation doesn’t seem to work either.