Looking at all of the photos of the 6 and 6+, I dont see the Home Kit app. I also watched them scroll through the phone in some of the hands on videos and i didn't see it there either..
You'll need to buy extra hardware to make use of it as well.
I was hoping I could set it up with a Raspberry Pi (which controls a few remote power sockets) but to no avail. Apparently it works with MFi products only..