We have a use case to put Alexa devices into many rooms and write custom Alexa skills to serve different responses and perform database updates based on which room they are in. As a result, we need to uniquely identify each Alexa in order to identify the room. We have look into various work around:
1) use "context:System:device:deviceId" which is specific to each skills and changes when the skills disable/enable.
2) use different userid to identify different Alexa but this would mean having many user accounts if the deployment is big
3) when Skill detects unknown "context:System:device:deviceId", expect user to use a certain utterance to provide the room information and register the new id in database.

However, none of these are scalable nor reliable so a real unique device ID for each Alexa would be desirable. Thanks!