I think you are projecting your own 'childhood' onto your children, Ansum. Where was your loving mother then? Why wasn't she following you to protect you from drinking in the streets at 14, and out with boyfriends at 16 until 2am? She tracks you now as an adult with kids?
- most parents know where their children are at 14yo!
Perhaps you are naive, or live in th safest part of the UK, but rape and attacks are rife here and 18 year olds are vulnerable and immature. I live in South London. Rapes and murders and bombs have been a fact of life here for decades. - I travelled through Kings Cross the day of the fire (half hour before), I worked in the City when the IRA were bombing St Mary Ax. 2 of my dc work in London. I worry, of course I do, but I don't track them. Yesterday, I knew they would be nowhere near the HoP but I dropped a text anyway.
And yes, when my children go clubbing into the city for the first few times, I will definitely be checking up on them to see if they are safe
Let me tell you what will happen when your dd reaches 18, if you control her so much. She gets a boyfriend. BF sees that mum has a tracker on her phone, so he gets himself put on too. DD thinks this is normal - after all, mummy does it (from a place of love!) and even lovely granny does it from the other side of the world. It's normal, it's sweet. Right?
BF tracks her to work, to the supermarket, to home. The one day she goes to the pub after work. Who is she talking too?
What is she drinking?
Ho much is she drinking? 
Next thing, BF doesn't want her going to the pub after work - it's dangerous, he doesn't like her drinking with others, the pub is not a nice area, why doesn't she come home to him where she is safe. Doesn't she like being with him? {angry] He loves her so much and doesn't want her hurt or in danger. Drinks' spiking happens, you know! It's all coming from a 'place of love'!
So now she can't go to evening drinks, leaving drinks, birthday drinks, anywhere in fact other than home or work. And she can't turn the fucking tracker off, because YOU'VE told her that would make her a BAD daughter! And because she doesn't realise that SHE HAS A CHOICE IN IT!
By all means, talk to your dd about dangers. Rape, murder, drinks spiking, yes they all happen. Controlling bastards like potential BF, and potentially you, happen much more frequently.