Here's the full changelog for the new firmware:
Firmware Version 18.104.22.1689
• Automatically Restore HomeKit Connection. Occasionally some ecobees could lose its connection to Homekit and have to be rebooted in order to re-establish the connection. This firmware update enables the ecobee to automatically reconnect without any user action.
• Wireless sensors with homekit enhancement. The wireless sensors now show up as accessories in the iOS Home app. Because of the dual functionality (occupancy detection and temperature sensing) of the sensors, each sensor will show up as two accessories.
• The usual background cleanup and stability. As always, to smooth things out for a better experience.
You can purchase the Ecobee3 Smart Thermostat from Amazon for $247.90. You can get an additional 2 pack of sensors for $58.61.