I run a Garmin Edge with Live Tracking function, but my wife usually stalks me with the Life360 app, which has free live 24 hour tracking. The newer Garmin have incident detection (it sends a text to a preset list of contacts), which works rather quickly, as I can attest from a minor spill on an ice patch last year. I was more irritated that it took some effort to cancel the alert. All of the Garmin features require the connect app to be running on your phone. Also, you can share your location from within iOS, so messages app can see location. Not sure of the setting for that latter, however. In my case, lots of redundant options gives my wife confidence she can collect the life insurance payout from my corpse.