Access Device Twin properties for IoT Hub input
It is possible to define custom properties for IoT Hub Device Twins (as documented here: https://azure.microsoft.com/en-us/documentation/articles/iot-hub-device-management-overview/) but these properties are not accessible in Stream Analytics jobs. Workaround is to define these properties in Reference BLOB Storage and JOIN it on device ID, but why not to have them in one place with (possibly) much faster access for large numbers of devices?
By user timestamped reference data, the reference data will be refreshed when the job is running.
Christian Eder commented
Afaik, this is no actual workaround, because the Stream Analytics Job will not react on changes to the reference data until it gets restarted. So, updating the device twin properties wouldn't affect a running Stream Analytics job...