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I was the same when I was a kid though, used to wander off without always telling my parents of my wherabouts, but being a parent myself now I have every reason to worry about where my kids are, especially with all the nonces and weirdo's roaming the country.
I want to give them the freedom to play out with their mates and have asked them so many times to tell me where they are going, though on some occasions they don't. They probably just get carried away with their friends and forget. As I've said this idea is purely a back up plan and reassuring for my wife and I as well as the kids.