I’ve somewhat under seige with constant attempts at scuppering my efforts to establish a smart home knocking me back at every step, I had hoped this app would be my saviour but as I’m an apple iCloud plus user I’m a bit stuck with the questions about servers as your app will not take iCloud for an answer. I’m not even sure the app I downloaded is the one I ended up with, because reading about the iOS companion guide really did feel like exactly what I need. Unfortunately whatever malicious actors are at work, these difficulties in assessing the service I need if anything confirms that it indeed what I need.
The iOS app talks to your install of Home Assistant.
You still need to have installed HA somewhere in your home.