Satellite device that lets parents track children

Developed to track dementia patients prone to wandering off, the device has seen sales increase since the abduction of Madeleine McCann in May.

A child being tracked wears a small black box which sends a signal that can be followed on a computer at home or work and is said to be accurate to within 13ft.

Mike Smuts, managing director of Blue Tree Services, which developed the system, said: "We have seen huge demand for this product. A lot of people set out for work first in the morning and the child only goes to school afterwards. People also like to use it when their child goes off on a school trip."

The basic system costs £19.95 a month to rent but there are extras such as a panic alarm and a movement sensor that can detect if the wearer has fallen or taken the box off.

A geographic boundary alarm can be set so that it is triggered if a child goes more than a certain distance from home.

A system with all these extras costs £39.95 per month. Mr Smuts said: "This is a robust and easyto-wear product. Parents can allow their children a little more freedom and at the same time manage their independence."

ButPenny Nichols of The Children's Society said: "As a society, we are in a real quandary over how much freedom to give our children. We want them to experience freedom of play but are increasingly frightened to let them out.

" Ultimately, parents have a responsibility to protect their children but a tracking system doesn't tackle the root causes of society's fears but rather encourages them."

She added: "Children are more at risk in the home than on the street."