Here is my tip on how to keep track of your kids whereabouts.
I'm not a big fan of cells as sometimes I feel there are more negatives then positives and still lot of unknowns. But I still needed to find a way, how to keep track of my son's whereabouts, when he goes out with his friends. On the list of presents he wanted for eid (Festival of the Fast Breaking) was a talkie walkie. In the end, I think it was one of the most useful presents we ever bought and I totally recommend it.
Talkie walkie is definitely cheaper to manage than cell. Because of the limited distance it broadcasts (not like cell), he has to keep around the house. We always make a signal check, when he arrives to his destination.
It is also very useful gadget even for family trips (to talk between cars, amusement parks - especially if you have only one cell in family), and a lot of fun for kids.
So if you are not as crazy about cells for kids as me, talkie walkie is a very good solution with multiple usage.
How do you keep track of your older kids, those who need more space than your garden can offer?