[dogscoff]

as they do have gps tracking devices you can purchase for implantation in your children to keep track of them

No they don;t.

How exactly would you power such a device? HOw would you recharge the batteries? WOuld you really want an orbital microwave transmitter implanted under your child's skin?

An idiot self-publicist "scientist" here in the UK (professor Kevin Warwick) tried to push these things a while back and caused a load of publicity, until it was discovered that the thing required a mobile phone in close proximity... utterly pointless tablod scaremongering, especially when there are far more important things to worry about, like book parasites....