All,
I have just posted a new topic about a project, ST_Anything, my son and I have developed to make using an Arduino with SmatThings as simple as we believe possible.
Check it out at Announcing the "ST_Anything" Arduino/ThingShield Project
Hopefully the ST_Anything project will at least provide some examples of what is possible. It also includes an upgraded Arduino SmartThings library which you can read about in the other post as well as on the GitHub repo at https://github.com/DanielOgorchock/ST_Anything
Dan