@jshimota beat me to it.. I was going to say OwnTracks is an app that just does geofencing and runs on both Android and iOS. It's a little on the complex side to configure but with the Hubitat driver you can have devices reporting directly to your hub.
I don't personally use this app just because I don't have any good uses cases for it (yet!). The reason I added geofencing to HD+ was really to replace the native Hubitat Android app which wasn't very reliable.
I'm not against supporting multiple locations in HD+ though.. I imagine each one would link to a Hubitat presence device.
