Homekit Compatibility Requirements
Originally SmartThings intended to be HomeKit-compatible, as did many other companies, but in March 2015 Apple clarified that any device that would be compatible with HomeKit had to have a particular encryption chip inside it. And for security reasons they also put limitations on some of the other features the device could provide.
So SmartThings, along with many other companies, decided not to sign up for HomeKit compatibility at the present time. The SmartThings hub that you bought will never officially work with HomeKit. It’s possible that some future SmartThings version might include HomeKit compatibility, but no plans at the present. So if you Google anything about compatibility, make sure it’s dated after March 2015.
So why SmartThings?
As for why you might want something like SmartThings in addition to HomeKit it’s because, as announced at WWDC 2016, HomeKit apparently is going for a fairly limited feature set. Lights, HVAC, locks, garage door control. All through either Siri or the new home app.
What’s missing? The most obvious is sensors that can trigger other events. For example, even though the HomeKit page mentioned this in one of the examples, it is not presently possible to have a battery-powered motion sensor trigger a light to come on in HomeKit. There is a Contact sensor where you can open the app and see how many times it was triggered that day, but you can’t get a notification when it’s triggered or have anything else happen like a siren go off or again lights come on.
(I know the screenshots make it look like this can happen, but it can’t. At least not so far. There’s a motion sensor associated with the echobee thermostat, but it only reports every 15 minutes.)
There is also no IFTTT integration, and not likely to ever be because of Apple’s security rules.
And as yet there’s no clear way do to add control of entertainment devices to your home automation rules. That could change. But SmartThings has it now through the harmony integration.
And the HomeKit rules engine is very simple. Basically your only available triggers are geopresence, time of day, and some HVAC values like thermostat setting.
In contrast, a full-featured system like SmartThings could let you have a rule like: if it’s after eight at night and John has been home for at least 20 minutes but Charlie is not home and it’s dark outside and someone is sitting on the couch in the living room turn on the speakers to level 10 and turn on the TV to ESPN.
Or notify me if it’s after 8 pm and the dog has not been fed twice today.
Or if I’m home and the Christmas tree pot is less than half full of water, turn off the tree lights, run water for 5 minutes (or until the pot is full) and then turn off the pump and turn the lights back on.
HomeKit can do some of that. But not all of it. (And I’m not saying it’s easy to do that with SmartThings, but it is possible.)
Smarter Home, not Smart Home
In short, HomeKit on its own will give you a smarter home in the sense that you will replace some of your existing devices like light switches and an air conditioner with a smarter device of the same type. Smarter meaning you can put it on time schedules and you can use your presence to have things automatically happen when you leave or arrive.
Full-featured systems like SmartThings are intended to give you a smart home. You will buy some devices you wouldn’t have had otherwise, mostly sensors, and those will allow you to set up multi level conditionals for complex rules.
Different people want different things
Do you need a full featured system? Only you can say. It’s likely that Apple will continue to add more device classes over time. But I think it’s going to be awhile before they have really complex logic. They want to keep it simple because they want to make theirs a mass market “set and forget” product.
I have HomeKit devices now, I like them, I intend to get more in the fall. But I also don’t need really complicated logic. Time schedules, Geopresence, and voice control will meet many of my household needs. But I still want battery-operated motion sensors to control the lights, and so far it looks like I’m going to need a second system just for that feature.