There’s a couple efforts going on right now to allow the use of Arduinos as cheap sensor/field nodes. These Arduino field nodes are cheap to implement because wireless modules like the nRF24L01 are super cheap, like $2 each. So the idea is that the sensor network is linked by cheap wireless modules. The missing piece is the ethernet connected gateway.
I see that SmartThings has a “SmartThings shield” for Arduino to make an Arduino talk to the SmartThings Hub. Can the ST-shield equipped Arduino act as the gateway Arduino to collect data from all the sensor nodes and present them as discrete sensors to the Hub? So I have 10 temperature sensors, 5 humidity sensors, some relay output Arduinos, some water sensing Arduinos all using nRF24L01 modules. They talk to a single Arduino that acts as the gateway to presents all this data to the Hub.
The shield and hub is pretty expensive. I wouldn’t mind it if I only have to buy one of each and then I can scale out my sensors. But it would defeat the purpose to have to buy a $30 shield for EACH sensor node. Especially since some sensor nodes are battery powered and sleep most of the time in a way that’s very easy to do with the nRF solution.