One way to utilize presence from Apple devices is with virtual devices in Homey and publish them to Apple Home with HomeKitty.
Instructions how to prepare HomeKitty.
First, create a virtual device with On/Off capability for each person:
Second, use HomeKitty to publish the devices to your Apple Home:
Now in Apple Home, prepare some home and away automations to switch the virtual device on/off for each person:
Finally create flows to update the presence of people in Homey:
Does this also work when I go out for a run wearing only my Apple Watch (and leaving my iPhone at home)?
If Apple Home is configured to use your Apple Watch as your presence, then maybe. That would be something that needs happen on the Apple Homekit framework.
I don’t have a watch so can’t test this.
So if you can configure your home/away status in Apple Home based on your watch, then this should work.
I have never been able to do that 
Anyone else?
I’m using this way of working almost the same for some years for a 4 person household. Works (almost) flawlessly.
I made it a little bit more simple because not all persons are configured in homey:
Define one virtual device “somebody home” and make HomeKit automations based on “first person comes home” and “last person leaves home”.
Also worth to mention is that you must have a HomeKit hub (HomePod, Apple TV or iPad) in your house. And iPads can’t be used in new HomeKit architecture.
Does anyone here know how to use the sleep mode of an Apple Watch to put Homey into sleep mode and not sleep mode? I can enable sleep mode, but I can’t disable it.
