We as a family all have an app called 'life 360'
it's a tracking app but gives such peace of mind.
It's free to use and we find it to be very accurate.
It even showed us when our daughters were recently in Greece,we could see when they were safely back at their hotel and such.
Each user has to consent to to using it so it's not a spying situation.
It updates all the time and shows their mobile phones current location, it also means that I dont ring them when I can see their driving.
I find the peace of mind to be invaluable and would still use,even if I had to pay for it.