Honestly I think IP communication is likely a better solution to interfacing with ST and my own projects. I have two of the Arduino shields and I’m still not using them. I have several ESP8266’s talking MQTT which integrate well into ST and also have conventional network access to other IP-based devices, and they do so at 1/10th the cost, maybe 1/5th the size, and lower power utilization than a Adruino Uno + ST Shield.
edit: Here’s an example of one of these projects, my IoTea kettle.