What I've done is set up an Arduino as a http server which supports inline sensor tags. These are commented tags hidden inside normal html files that the server hosts. When a requested html file is returned it is parsed on the fly and any sensor tags are concatenated with the matching sensor data.
This allows the server to serve up pretty pages which abstract the complicated details of accessing the sensor. The server can be visited like a local web server or the chumby can access it and use that data in it's widgets.
The Arduino is not the worlds best http server, but as a simple http sensor server with limited connections, home cloud use is perfect.
Now on the chumby side a special get file request is sent to the server which returns the requested remote sensor or device data. Data can be parsed from returning html files, since I leave in the original commented sensor tags with the data. Files named to the sensor tag name simply return the sensor data text.
Sensor and other data devices then can be made generic and auto detectable by a Chumby on a local wireless network.
Chumby outside temp sensor, baby monitor, front door monitor, etc... things useful at your bedside.