I like using Apple HomeKit on iPhones, iPads, and Macs as a simple, clean GUI. In order to do so, however, you’ll need to run HomeBridge on an always on computer in your home, like a Raspberry Pi. There are two Hubitat Plugins for HomeBridge, one from @dan.t and another from @tonesto7. Both are popular amongst the community users and both work well.
There is also another Mobile Phone App called “The Home Remote” that works well on iOS, and requires no custom code on Hubitat. It simply uses the built-in Maker API app for connectivity.