SmartThings used to sell an Arduino shield called the ThingShield. It was Zigbee based and is what prompted my son and I to write ST_Anything. It is very hard to find used ThingShields these days, and I am guessing that their days are numbered… Once the Groovy IDE gets shut down in sometime in 2021, I am not sure if there will be a way for them to still function properly. (Note: I do have the ThingShield working on Hubitat! 
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In addition to the old Zigbee ThingShield, there are two other Zigbee devices that community members have created and offer to the community. The first is @iharyadi’s Environment Sensor EX and the second is @drandyhaas’s Mona Lisa. Both work very well, however I do wonder what will come of them once the ST Groovy IDE is shut down next year. Hopefully creating custom drivers for whatever replaces the current Groovy ST IDE for hub-connected devices will not be too hard.