Subscribe to IoTHub messages by device or message criteria
Similar to message routing but client driven.
Currently clients have to receive all messages and filter out the ones they don't want. This is very inefficient, for example in the case where you might send a command to a particular device and just want to check the value of the next message sent to IoT Hub from that device. Temporary subscriptions (even if limited to a short period) on device or message value would help a lot in such situations.