The Aqara HomeKit hub is a really interesting device. I spent the last 24 hours getting familiar with what's possible and what isn't.
What it is:
By far the least expensive and most comprehensive official HomeKit hub so far. The Xiaomi Mijia and Aqara devices are very good quality for the price, and pairing them to an actual Xiaomi Aqara hub is a breeze. The devices literally pair within seconds, every time. No need to tap the pairing button to keep them awake, as is necessary with ST and HE. I found that even though the devices have an infamous reputation with developers that have suffered the significant variations from one Xiaomi device to another, the Aqara Hub doesn't care. It paired both Aqara and Mijia branded devices with great ease.
The Hub is small (roughly the size of a hockey puck and about 1/3 thicker). Although I had hoped to have received one with a North American plug, I did not, and instead a free plug adapter to go from the three prong Chinese plug to a non-polarized North American plug was included in the shipping envelope. The hub has a lighted ring that can be used to display just about any color you want, or it can be turned off via HomeKit. The speaker for the alarm has selectable sounds, custom sounds (android app required for uploading MP3 files), and by assigning a Xiaomi trigger device, it can be used as a doorbell too.
What it is not:
The hub can be accessed via app only. You have a choice of the Xiaomi Mi Home app or the Aqara Home app. The Mi Home app allows the most control over the device, but it is not pretty and not properly formatted for large modern screens. There are significant anomalies in the UI that make the use of the Mi Home app very frustrating, not to mention the weak UX. The Aqara app on the other hand is nicely designed and has no such display issues, but it's confusing that when you switch the location from United States, to Europe, the UI and capabilities significantly change in the same app. When the app is set to Europe, it is a full HomeKit app. This has advantages if you want to use HomeKit for automations, but that's the rub. You can only create HomeKit automations and HomeKit Scenes to their full extent when the app location is set to Europe. When set to United States, Mainland China or Other Region, you have IF-THEN automation capability right in the app allowing more control over what the hub does. Unfortunately, those automations are restricted to Xiaomi devices and the hub. The only way to automate between other non-Xiaomi devices and Xiaomi devices attached to the Aqara Hub is via HomeKit automations.
Limits:
While it's possible to set the alarm and doorbell sound and level, that functionality isn't available in the Aqara Home app. This presents a minor problem if you decide you want to change it after you have everything setup in HomeKit. The Mi Home and Aqara Home apps cannot access the hub at the same time. So it is necessary to reset the HomeKit pairing so the Mi Home app can connect to the hub. This does allow the hub to still be exposed to HomeKit, but in a more limited fashion. For example, there isn't an alarm arm and disarm capability in the HomeKIt layer that is exposed via the Mi Home app, but it is there, only it's tied together with the light ring settings in HomeKit for some reason. Getting things to work in HomeKit with the Mi Home app I found to be very challenging.
So once you change to the Mi Home app and set your sounds and volume levels, you can switch back to the Aqara Home app with little issue. It has a "Bind Hub" function that seems to work fairly well. Only failed once, and I just repeated it with success. But, this means your HomeKit automations will all be broken or will disappear when you have to reset the HomeKit settings to pair with the Mi Home app. That part is a real mess, and I do hope that is resolved in later app and firmware updates.
Controversy:
So I had three things in mind when I bought this hub, but I think I'm probably going to get more than I expected in the long run.
-
I wanted to play with a new toy that would make me look at HomeKit differently.
-
I wanted to use this as a doorbell. This I thought (hoped) might be possible by triggering a virtual switch exposed to HomeKit. No such luck. While you can turn other HomeKit devices on/off from an Aqara scene, you can only trigger an event on the Aqara Hub by way of another Xiaomi device paired with the hub. For me, this wasn't such a big deal, since I was already triggering my doorbell sounds via an Aqara contact sensor, where I soldered two leads to the reed switch and then attached them to wire running up to a standard doorbell button.
-
I wanted to use this as a supplemental alarm siren if possible. But, how was I going to trigger the alarm if only Xiaomi devices directly paired to the hub were able to do that? I thought about using the second Xiaomi dual relay I have on the way. Once it's exposed to HomeKit, I would simply have to operate it to trigger the siren, but not only did that seem like a waste of a decent dual relay, it would still leave me with the problem of triggering a remote siren from my closed platform iSmartAlarm system.
The answer was to remove my Xiaomi Mijia door/window sensors from Hubitat Elevation and pair them directly with the Aqara Hub. This is where that decision is a controversial one. In order for HE to be able to still use the contact sensors for my door announcements, prevention of locking when the door is open, etc., it was necessary to go back to using HomeKit automations to link contact sensors with HE virtual switches exposed via Homebridge.
Now I had done this in the past and the results were very unreliable, and down right frustrating. This time it's very different though. @dan.t 's version of the Homebridge app via Maker API is so fast and reliable, that I think it's going to workout just fine this time around. So I have a Mijia button hidden away for emergency disarm, and door/window sensors paired directly with the Aqara Hub, then synced with virtual switches in HE via HomeKit automations. The results are quite impressive. I cannot tell the difference from when the door/window sensors were paired directly with HE. Hopefully it stays that way and this little experiment is a success.
Note of interest- The great work done with the Xiaomi button driver for HE actually exposes 3 addtional button presses that the Aqara Home app does not. They support one-click, two-clicks and long-click only*.*
Conclusion:
I'm giving the Aqara Hub HomeKit edition a 
for its ease of use (for non-technical HomeKit only users), but it definitely needs to be further simplified, and the missing sound and alert volume settings really need to be added to the Aqara Home app. For the $40 US I paid, I'm quite happy with this, and I hopefully will not have to deal with any connection issues like some of the Z-Wave doorbells seem to have. Having this function as a supplemental siren is a nice bonus considering the low price. However, Android-only users will have a significantly more difficult time integrating this with HE, and if I didn't already own an Apple TV 4, then the cost savings would be more than eaten up in purchasing one, just so I could run HomeKit automations.
