I've had an Ecobee 3 plugin working locally for a couple months now. I planned to share it earlier, but I got sidetracked with work on the Nissan Leaf plugin. That is temporarily out of the picture, though, until Nissan secures their API.
This Ecobee 3 plugin is working pretty well for me, though obviously a sample size of one doesn't really mean much.
Known issues:
- Only supports one Ecobee thermostat (but supports multiple remote sensors on that thermostat) Update: no longer true!
- Read-only; only reads information from the thermostat and sensors; no functionality yet to make any changes. This is just something I haven't needed yet, though I do plan to implement it. Update: no longer true!
- A bit touchy about authentication; if you mess with the plugin much, you may find that you have to reauthenticate on the Ecobee web site and refresh your tokens before the plugin will work again. (Instructions for this can be found on the plugin configuration screen.) Update: no longer true!
Plugin is located here: https://github.com/jdhorne/indigo-ecobee-plugin
Once you install, you'll need to get a PIN from the plugin configuration page and enter it on the Ecobee web site to authorize access. Then just go back to the plugin configuration screen, click "refresh tokens", and you should be able to add your thermostat (and then your remote sensors).
Good luck, and let me know if you have any problems!
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UPDATE 2016-06-22, version 1.0.0 (yay!):
* first support for two-way control (i.e. control the thermostat from Indigo; thanks rapamatic)
* first support for reporting of auto home/away events on Ecobee 3 (via new "autoHome" and "autoAway" boolean states)
* bugfix: authentication tokens weren't being saved beyond first retrieval (thanks rapamatic)
UPDATE 2016-04-27, version 0.1.0:
* Now supports Ecobee Smart thermostats (thanks to user rapamatic) in addition to Ecobee 3
* Now supports multiple thermostats