Just a heads up the Xiaomi zigbee smart home devices do work with SmarThings and they are easily the cheapest.
http://xiaomi-mi.us/mi-smart-home/xi...reless-switch/
http://xiaomi-mi.us/mi-smart-home/xi...indow-sensors/
http://xiaomi-mi.us/mi-smart-home/xi...midity-sensor/
http://xiaomi-mi.us/mi-smart-home/xi...upancy-sensor/
I was skeptical at first so I just ordered the switch. It arrived yesterday. Pairing wasn't overly difficult. Works great. Will be ordering more.
Shipping cheaper from http://www.gearbest.com/ Although I dont recommend the cheap shipping. Might not see your stuff for a few months