Are you already running Homebridge on a Raspberry Pi or similar?
If yes, using Homekit for location should be fairly simple. I am sure @SmartHomePrimer can explain it.
If not, you might prefer to simply use Locative for iOS. It is a very lightweight application, does not use hardly any battery power, easily integrates with Hubitat via the Maker API, and runs 100% local on your phone - no cloud servers involved, except Hubitat's.
