Ecobee announces a firmware update for the Ecobee3 smart thermostat-- one adding HomeKit support to both the thermostat and the individual remote sensors making the system.
The Ecobee3 uses additional remote sensors to keep track of ambient temperature around the house, as well as detect motion in different locations. Firmware version 3.7.0.969 allows users to access individual sensors directly from the iOS Home app. Since the sensors feature dual functionality (occupancy detection and temperature sensing) each sensor appears as 2 accessories on the app UI.
Of course, HomeKit support also adds voice-based control via Siri, meaning users can ask Siri for the temperature of specific rooms.
The latest firmware version is currently rolling out to customers. There is no way one can manually update the Ecobee3 firmware, but one can contact Ecobee customer support and request the update to be pushed to their account.