I came across this component (link below) which was added to Home Assistant fairly recently and was really hoping to discover the same functionality for the Hubitat now that I've switched to it. My Ecobee is that last device I have that's still cloud connected and I would be thrilled to be able to bypass that through the use of Homekit.
Is there presently support for this and I'm just not seeing it or is that something that could be added in the near future?
This integration works really well if you have a Raspberry Pi running Homebrige.
I use it multiple times every day.
Raspberry Pi is cheap and Homebridge is easy to install.
I think this is the other way around. Get devices linked to Homekit published in HomeAssistant. Looking at the code right now to see if my assumption is right
Oh this does go backwards.
To each their own I suppose. 
HomeKit is at the top of my pyramid of integration and control.
No matter what, your Ecobee will always be cloud based. Homekit just exposes it on your phone but everything still goes through the cloud. You wouldn't make your Ecobee magically be local
That's actually incorrect, see here:
https://www.reddit.com/r/ecobee/comments/7glzjd/tilhomekit_control_of_ecobee3_works_without/
It is a very interesting implementation. It works based on the homekit-python library
this library can create it's own HomeKit Controller instance, think of it as another iPad or Apple TV not linked to your iCloud account.
You can then discover any IP based device on your network that has HomeKit support and link it to that controller created by that library. You don't control it through your phone directly. You actually have to link each device twice: To your phone and to your controller and you have to do that for every device you wish to control.
Let's say you change the temperature on your Ecobee, here is how the flow is:
On your iPhone change temperature in the Home App ----> Home app sends message to Ecobee to change temperature ---> Ecobee sends message about temperature change to this Controller ---> The controller informs HASS
Technically, it would be possible to get something like this done for Hubitat, but it is quiet some effort. We would need to program a new "man-in-the-middle" application that implements this controller. This application also needs a User Interface (website, console, etc...) as you need to interact with the devices during the pairing.
a) you need to select the device you want to pair
b) you need to enter the pairing code that is given by the device
Then you would need to develop an interface to Hubitat, a Hubitat app that interfaces with that application and a slew of virtual drivers that are then used within Hubitat.
For sure nothing simple and quick.
I'll think about but I am not sure that I have enough free time right now to get started on this endeavor. Nor am I sure that all of this effort is worth it.....
I'd use it for sure. I have a couple HomeKit only doors that I get synced to Hubitat via virtual switches and HomeKit Automations and Homebridge. It's a bit fragile - if you have to re-pair Homebridge you have to rebuild the automations.
I'd also like to be able to add HomeKit devices to Hubitat. This way I could use Aqara Hub with devices like Aqara Vibration Sensor and Xiaomi Smart Plug (ZNCZ02LM) connected to the Awara Hub.
Direct connection of Aqara Vibration Sensor to Hubitat does not work at all (it seems to lose the connection all the time).
Also I remember reading somewhere that direct connection of Xiaomi Smart Plug to Hubitat is not recommended since it can mess up the ZigBee mesh.
Not sure about the outlet causing issues. I won’t buy a Xiaomi outlet because I’m in Canada. Their outlet for China, Australia and New Zealand can only accommodate non polarized two prong plugs, which is what Japan uses. if they finally release the North American version, then I’ll try it out.
In regard to the Xioami Aqara HomeKit hub and Xiaomi Aqara and Mijia sensors, this is exactly what I do now.
I’ve changed all my Xiaomi Mijia, and one Aqara contact sensors over to the Aqara HomeKit hub, and I sync them with HE virtual switches using HomeKit automations. Works great. The sensors pair very easily to the Aqara hub and never drop. Response time is very fast using @dan.t ‘s Homebridge MakerAPI Plugin, and the occasional false positives I was getting when the contact sensors were paired directly to HE are now gone.
However, for motion sensors and everything else, I pair directly to HE using @veeceeoh ‘s excellent drivers for Xiaomi devices. I have a Xiaomi vibration/tilt sensor too, but have not paired it with anything yet. I will first try HE directly, but if I do have any trouble, I can just use the Aqara HomeKit hub.
It’s a nice option to have available. I know some people don’t like having a bunch of hubs, but I actually prefer it, as long as they effectively communicate with each other, I find it makes things easier and opens more opportunities for cool and low cost stuff.
I have no idea about the Xiaomi Smart Plug ... but would also like to be able to add HomeKit devices to Hubitat as Hubitat devices. I've implemented using HubConnect Server, so if another approach would allow such "backward" integration, I'm quite interested.
Just my 2 cents, and to bump the thread!
Adding the HomeKit Controller option to Hubitat would open the doors quite a bit, and I think that also falls in line nicely with the ideals of Hubitat (Local, Secure) as HomeKit is a local protocol.
It could provide access to just about any device that has the "Works with HomeKit" logo, and there's a lot!
Legrand, IKEA, Xiaomi, Fibaro, Loxone, KNX, ... just to name most of the EU's players... and I don't want to go back to Home Assistant and it's volatile environment...
I've also looked at the feature requests list and the HomeKit Controller would solve a "few" of those as well 
Same idea, but with less Apple devices on the network
Most of Europe uses Android devices and has 0 Apple devices (and the usually cost an arm & a leg), this option would benefit those who are taking a step by step approach on a budget 
Sweden is Europe and Apple users are far more more common here.....
Sweden is part of Europe, not Europe itself
And I'd like to see some statistics about how many iPhone users have other HomeKit Controller (AppleTV, ...) devices in their homes.
It is a must! All the major European "smart home center" producers (Fibaro, Zipato, etc.) misses this integration; only Homey is working on it.
A lot of members from our thematic Facebook group mentioned that they moved to Homey because of HomeKit controller integration.
Download the Hubitat app
