A new service based on satellite tracking technology enables parents to pinpoint their children's current location to within four metres (13 feet).

The Blue Ranger starter pack, which was largely developed by Irish engineers, uses a small global positioning system (GPS) transmitter, about the size of a packet of cigarettes, which can be carried in a child's pocket or schoolbag. Parents can then use their internet-connected PC to plot the child's exact location on a map.

UK-based Blue Tree Services has launched the service in time for the back-to-school market and is charging €29 per month for it.

Blue Tree managing director Mike Smuts says the service is a version of its personal tracking system launched in March which provides a number of additional features such as being alerted if a child leaves a defined area (a so-called "geo-fence"), a panic alarm and a movement sensor which can tell if the unit has been subject to a shock or fall.

In the wake of cases such as the abduction of Madeline McCann, many parents would clearly avail of any technological edge that they feel can make their kids safer. But other parents and even civil liberties groups would question the desirability of tracking their children's movements from morning to night.

"If you take out insurance against getting cancer, people don't call you a hypochondriac, so why should they call you paranoid for using a tracking device to give you the comfort of knowing where your children are?" Smuts asked.

TJ McIntyre, chairman of lobby group Digital Rights Ireland, which has campaigned against digital surveillance in a variety of formats, says his group would be less concerned about parents tracking the movements of children than if a State body was doing so. "We still believe that safeguards need to be in place so that the data is not being used inappropriately," he said.

The Blue Tree service encrypts the information being sent back to its monitoring centre so it cannot be intercepted by third parties.