Well. it's up to me as a parent to not abuse my children's freedom, regardless of the technology available to me.  my son is 22, and he can remove the app from his phone at any time... he chooses not to because he trusts me not to snoop on his life, and I sure don't... I never looked at where he was since he was in his mid-teens, and I never abused his trust and his freedom. The only time I used the app in last few years - was when I woke up at 5:00 am, and his car was not in our driveway.  I looked at the map and recognized that he was at his GF place and went back to bed.  Turned out he was too shitfaced after the bar crawl to drive and crashed at her place and didn't want to wake us up with a text or a call.  if I didn't have the app, I would've been worried and probably initiated the contact that was unnecessary.

My almost 17-year-old daughter has the absolute freedom to stay up and out as long as she wants as long as I know ahead of time about her plans. If she tells me she will be home after 11, and she is not home after midnight, I do want to keep a closer track of her whereabouts. She is a teenage girl and I am a little more risk-averse in her case for now.  

My 87-year-old mother drives herself and my 93-year-old dad to their appointments and gets groceries... they don't speak much English, and sometimes they can't hear the phone ringing, ... so I do keep track of them with alerts when they leave or arrive to their usual destinations (grocery store, dr offices, my sisters place, my place and their place) saved in the app.  and I know that if they left one saved destination and did not arrive to another saved destination in a reasonable time, I need to initiate contact