When we had to track teenagers' nightclubbing whereabouts (they're adults now), we did the following: 1) made sure we'd written down their mobile phone-numbers (obviously) 2) remembered their names/addresses (obviously) 3) told them to leave their mobiles switched ON all the time (they'd have done that anyway to keep up with Social Media) 4) Sent them a text every hour on the hour and they'd have to reply 'OK'. We'd reimburse them the money for the texts (nice little earner if you're on a plan...). Side-effect: it boosted their self-esteem (wow, getting messages all the time - she must be popular). Was that asking too much? Fast forward to our current lockdown and the way to handle self-quarantine: 1) as above 2) as above 3) as above 4) get info from cellphone-towers to check which one they're logged in. If, for example, someone is in self-quarantine at an Auckland campground and all of a sudden's logged into the Gisborne cell-tower, that would be an indication that they're elsewhere - or that the phone had been stolen. Note that in the case of traffic accidents police already get the info from cell-towers, so they can determine if the driver - according to their phone - was in the area, logged on and texting. Piece of cake for them, according to TVNZ. BTW, there is no need for name-matching: the rental-car companies do that anyway, so the user's name could stay anonymous - until police very kindly ask/beg cap in hand for it to be released. Tom Butz.