Hi,
Since I already have a Raspberry Pi and not an Arduino, I will be working on building basically the same using the RPi instead and having Smartthings communicate with the Pi over http (on the local network). I’ll make sure to document and post back with results.
I will basically follow these instructions: How to Control Power Outlets Wirelessly Using the Raspberry Pi – Sam Kear, modify the php code for my purposes and create device types as needed (right now I only have one of these to control: http://www.amazon.com/gp/product/B012NB65AW?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s00). Also for a quick and dirty http get momentary switch see thread below. I built the device type so I can call a locally hosted php page which then arms my lifeshield alarm, this would essentially work the same way.
If anyone has any suggestions, please let me know. Thanks.